Pr1.5 tmm nexthop (#10745)

* TrafficManagement: flat unified cache + persistent next-hop overflow store

Reworks the TrafficManagementModule cache layer (policing behaviour unchanged
from upstream) and adds a routing-hint overflow store:

- Flatten the ring: replace the cuckoo-hashed unified cache and the bucketed
  PSRAM NodeInfo index with plain flat arrays + linear scan (same idiom as
  WarmNodeStore). At LoRa packet rates an O(n) scan of the cache is negligible,
  and it removes a large amount of hashing/displacement complexity. The cache
  entry is 11 B; timestamps use a uniform +1 presence-offset so a 0 byte always
  means "empty" across every sub-store. Adds rebaseEpoch() so cached state
  survives the ~19 h relative-timestamp horizon instead of being flushed.

- Next-hop overflow cache: setNextHop/getNextHopHint store a confirmed last-byte
  relay for a destination, written only from NextHopRouter's ACK-confirmed
  decision (and mirrored from TraceRoute). NextHopRouter::getNextHop falls back
  to this cache when the hot NodeDB has no hint, so DMs/relays to long-tail
  nodes keep routing after the node ages out of NodeInfoLite.

- Persistence: preloadNextHopsFromNodeDB warm-starts the cache from persisted
  NodeInfoLite hints on first maintenance pass; next_hop entries are kept alive
  across the maintenance sweep (no TTL) and never clobbered by a stale preload.

All packet-policing logic (rate limit, position dedup, unknown-packet drop,
NodeInfo direct response, hop exhaustion) is the existing upstream behaviour,
untouched. HAS_TRAFFIC_MANAGEMENT defaults on so the module is compiled in. (see note).

Tests: upstream policing suite now actually runs (adds the MeshTypes.h include
that gates HAS_TRAFFIC_MANAGEMENT) plus 4 next-hop tests. Role-aware throttles,
politeness, precision clamp, port-interval and mesh-radius gating — and the
rate-limit >255 saturation fix — are deferred to the advanced-TMM branch.

Note: default dedup movement grid moves to ~91m, which also means 1.5km required to end up with the same signature position - coarser and therefore further than before.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* TrafficManagement: fix cppcheck constVariablePointer warning

`node` in preloadNextHopsFromNodeDB() is never written through — mark
it const to satisfy cppcheck's constVariablePointer check in CI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Add multi-hop NextHop recovery tests and unit tests for routing reliability

- Introduced a new test suite for multi-hop NextHop directed-message delivery and relay recovery in `test_nexthop_multihop_recovery.py`. This includes tests for end-to-end delivery and recovery after relay drop.
- Implemented unit tests in `test_main.cpp` for NextHop routing reliability mitigations, covering:
  - M1: Ambiguity-aware last-byte resolution.
  - M2: NextHopRouter's strict-neighbor gate and hop limit checks.
  - M3: Route-health freshness and failure decay.
- Enhanced mock classes to facilitate controlled testing of node behaviors and routing logic.

* grafting fixed

* Address Copilot review for PR #10735 (NextHop improvements)

- docs/nexthop-routing-reliability.md: update status from "no code
  changes yet" to reflect that mitigations and tests are implemented

RAM pressure and MIGRATION_VERBOSE concerns addressed upstream in
PR2.5 (per-platform TRAFFIC_MANAGEMENT_CACHE_SIZE) and PR2 (verbose
default=0) respectively; (0,0) sentinel fixed in PR2.5.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* CI: fix cppcheck constVariablePointer and test include path

- NextHopRouter.cpp: qualify two RouteHealth *h locals as const — only
  read for stale-route checks, never mutated through the pointer
- Router.cpp: qualify meshtastic_NodeInfoLite *node as const in
  shouldDecrementHopLimit — only read for favorite/role predicate
- test_position_module/test_main.cpp: change bare PositionModule.h to
  modules/PositionModule.h — build_flags sets -Isrc, not -Isrc/modules,
  so the bare form fails to resolve in the native PlatformIO test env

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* WarmStore: cache device role + protected category in last_heard low bits

Steal the low 6 bits of WarmNodeEntry.last_heard to carry an evicted node's
device role (4 bits) and a protected category (2 bits) for the hop-trim path,
at zero record-size cost (entry stays 40 B; no RAM/flash growth). The high bits
remain a real unix-seconds timestamp, quantised to 64 s — ample for warm LRU
ordering of long-tail nodes.

- absorb() packs role/protectedCat; place()/ring replay store the raw word so
  metadata round-trips through flash. LRU compares masked time (warmTimeOf).
- take() rehydration masks the metadata bits and restores the cached role so a
  re-admitted node isn't stuck at CLIENT until its next NodeInfo.
- NodeDB classifies the category (favorite/ignored/verified -> Flag;
  tracker/sensor/tak_tracker -> Role) at each eviction site.
- WarmNodeStore::lookupMeta() exposes role/category to consumers.
- Bump WARM_RING_MAGIC (WRNG->WRN2): old rings read as erased and rebuild;
  warm data is a non-critical evictee cache, so discard-on-upgrade is safe.

Tests: test_warm_store 11/11 (new meta round-trip + quantisation-aware ordering);
NodeDB compiles (test_nodedb_blocked 4/4).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* WarmStore: migrate v1 rings/files by discarding last_heard, not the data

Previously the WRNG->WRN2 magic bump treated old rings as erased, discarding all
warm entries — including the PKI public keys that let evicted nodes keep
decrypting DMs. Instead, read v1 (WRNG / WRM1) records and keep each node's
identity + public key, discarding only last_heard (its low bits would otherwise
be misread as the new role/protected metadata). Records re-rank and re-learn
their role on next contact.

- Ring backend (nRF52840): ringReadHeader accepts both magics and reports v1 via
  an out-param; replay zeroes last_heard for v1 records. If the active head page
  is v1, force a rotation so new v2 records never land in a v1-headered page
  (which would discard their freshly-set role on the next load). Legacy pages
  convert to v2 as the ring rotates.
- File backend (warm.dat): bump WARM_STORE_MAGIC WRM1->WRM2; accept WRM1, verify
  CRC against the stored bytes, then discard last_heard and mark dirty so the
  next save rewrites as v2.

Tests: test_warm_store 12/12 (adds test_ws_v1_migration_discardsLastHeard:
key survives, role/protected reset).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* WarmStore: guard role bit-width + test eviction carries role/protected

- static_assert that the device role enum still fits the 4-bit warm metadata
  field (WARM_ROLE_MASK); fails the build loudly if a new role is added past 15
  rather than silently truncating role on eviction. (Max role today = 12.)
- Add test_migration_carriesRoleAndProtectedIntoWarm: a demoted TRACKER lands in
  the warm tier with its key, role=TRACKER and protected category=Role; a demoted
  CLIENT carries role=CLIENT/None. Exercises the NodeDB eviction path +
  warmProtectedCategory classification (the warm-store unit tests only cover
  absorb() directly).

Tests: test_nodedb_blocked 5/5.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix copilot comments

* fix(test): restore #if HAS_TRAFFIC_MANAGEMENT guard in TMM test

The rebase onto PR1.5 lost the top-level HAS_TRAFFIC_MANAGEMENT guard
that PR1.5 introduced, leaving the #else/#endif tail orphaned and
causing compile errors on non-TMM builds.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/mesh/NodeDB.h

@@ -115,6 +115,20 @@ uint32_t sinceLastSeen(const meshtastic_NodeInfoLite *n);
 /// Given a packet, return how many seconds in the past (vs now) it was received
 uint32_t sinceReceived(const meshtastic_MeshPacket *p);
 
+/// Outcome of mapping a single on-wire last-byte (next_hop / relay_node) back to a full NodeNum.
+/// Because the wire only carries the last byte of a 32-bit node number, the mapping is ambiguous on
+/// dense meshes (the "birthday problem"). Callers must treat Ambiguous and None as "don't trust it".
+enum class LastByteResolution : uint8_t {
+    None,      ///< no relevant candidate node has this last byte
+    Unique,    ///< exactly one relevant candidate -> `num` is valid
+    Ambiguous, ///< two or more relevant candidates collide on this byte
+};
+
+struct ResolvedNode {
+    LastByteResolution status = LastByteResolution::None;
+    NodeNum num = 0; ///< valid only when status == Unique
+};
+
 /// Given a packet, return the number of hops used to reach this node.
 /// Returns defaultIfUnknown if the number of hops couldn't be determined.
 int8_t getHopsAway(const meshtastic_MeshPacket &p, int8_t defaultIfUnknown = -1);
@@ -331,6 +345,23 @@ class NodeDB
     /// with no allocation side effects (unlike getOrCreateMeshNode).
     uint32_t hotNodeLastHeard(NodeNum n) const;
 
+    /**
+     * Resolve a single on-wire last-byte (e.g. next_hop / relay_node) back to a unique full NodeNum,
+     * detecting last-byte collisions instead of silently picking the first match. A 1-byte id only
+     * needs to be unique among a node's plausible relays, not the whole mesh, so we scope the search:
+     *  - requireDirectNeighbor == true  : candidates are direct neighbors (hops_away==0) heard within
+     *                                     NEXTHOP_NEIGHBOR_FRESH_SECS. Use on the SEND path.
+     *  - requireDirectNeighbor == false : also accept favorites and router-role nodes (unknown hop
+     *                                     distance allowed). Use when learning / preserving hops.
+     * Ignored nodes, our own node, and the broadcast/0 sentinels are never candidates. On a tie the
+     * result is Ambiguous (no tie-break) so callers fall back to flooding rather than misroute.
+     */
+    ResolvedNode resolveLastByte(uint8_t lastByte, bool requireDirectNeighbor);
+
+    /// Convenience wrapper around resolveLastByte(): true iff exactly one relevant candidate matches.
+    /// Ambiguous and None both return false (the safe answer for learning / hop preservation).
+    bool resolveUniqueLastByte(uint8_t lastByte, bool requireDirectNeighbor, NodeNum *outNum = nullptr);
+
     // Thread-safe satellite-map accessors. Return false if absent or the
     // corresponding DB is compiled out.
     bool copyNodePosition(NodeNum n, meshtastic_PositionLite &out) const;