docs: move the firmware design docs to the documentation site (#11488)

The five documents under docs/ were written in this repo while their features
were developed. Four of them describe shipped, upstream behaviour and belong on
meshtastic.org, where users and client authors will look for them:

  traffic_management_module.md    -> configuration/module/traffic-management
                                    + development/reference/traffic-management-internals
  node_info_stores.md            -> development/reference/node-info-stores
  mesh_beacon_module.md          -> configuration/module/mesh-beacon
                                    + development/reference/mesh-beacon-internals
                                    + development/device/mesh-beacon-client-interface
  lora_region_preset_compatibility_client_spec.md
                                 -> development/device/region-preset-compatibility

Each is split by audience: settings pages carry the config surface in user
terms, reference pages carry firmware mechanism, and the device pages carry the
protocol a client app speaks. The region-preset spec always said it should
graduate out of this repo once its protobuf landed upstream, which it has
(FromRadio.region_presets, field 19).

nexthop-routing-reliability.md is not documentation - it is a working document
with a mitigation plan, a "files to modify" list and commit sequencing. Its
mitigations shipped in #10745, so the plan is history and the analysis is
superseded; it is dropped rather than published.

Comments that cited the deleted files now point at the published pages, and the
NextHop test header cites #10745 instead of the deleted plan.

src/modules/TrafficManagementModule.cpp

@@ -586,7 +586,8 @@ void TrafficManagementModule::reconcileNodeInfoFromNodeDBLocked()
 
     // Membership refresh (this hourly pass owns it): clear every isMember bit, then re-mark from
     // both NodeDB tiers. Runs AFTER seeding so the upsert still sees last pass's bits (spareMembers).
-    // Cost/lag rationale in docs/node_info_stores.md "Consistency with NodeDB (anti-entropy)".
+    // Cost/lag rationale in https://meshtastic.org/docs/development/reference/node-info-stores "Consistency with NodeDB
+    // (anti-entropy)".
     for (uint16_t i = 0; i < nodeInfoTargetEntries(); i++)
         nodeInfoPayload[i].isMember = false;
     for (size_t i = 0; i < nodeDB->getNumMeshNodes(); i++) {
@@ -729,7 +730,8 @@ bool TrafficManagementModule::copyPublicKey(NodeNum node, uint8_t out[32], bool
 {
     // Same enable gate as the write-through hooks and maintenance: a disabled module stops
     // updating and sweeping the cache, so its frozen contents must not keep feeding PKI key
-    // resolution either. Enforces the "superset only while enabled" corollary (node_info_stores.md).
+    // resolution either. Enforces the "superset only while enabled" corollary
+    // (https://meshtastic.org/docs/development/reference/node-info-stores).
     if (!moduleConfig.has_traffic_management)
         return false;
     if (!nodeInfoPayload || node == 0 || !out)
@@ -1514,7 +1516,8 @@ bool TrafficManagementModule::shouldRespondToNodeInfo(const meshtastic_MeshPacke
 
     // Throttle the spoofed reply (per requester + per target + 1 s global floor; checked here so a
     // request declined above never spends the budget). false forwards the request instead of consuming
-    // it. Rationale in docs/traffic_management_module.md "Throttling direct responses".
+    // it. Rationale in https://meshtastic.org/docs/development/reference/traffic-management-internals "Throttling direct
+    // responses".
     if (!directResponseAllowed(getFrom(p), p->to, clockMs())) {
         TM_LOG_DEBUG("NodeInfo direct response throttled for 0x%08x; forwarding request", getFrom(p));
         return false;

src/modules/TrafficManagementModule.h

@@ -33,7 +33,8 @@
 
 /// Packet inspection and traffic shaping: position dedup, per-node rate limiting, unknown-packet
 /// filtering, NodeInfo direct response, and the next-hop/role overflow caches. One flat 10-byte
-/// unified cache backs all per-node features; see docs/node_info_stores.md for the store overview.
+/// unified cache backs all per-node features; see https://meshtastic.org/docs/development/reference/node-info-stores for the
+/// store overview.
 class TrafficManagementModule : public MeshModule, private concurrency::OSThread
 {
   public:
@@ -144,7 +145,8 @@ class TrafficManagementModule : public MeshModule, private concurrency::OSThread
   private:
     // 10-byte packed entry, all platforms. Tick stamps are free-running modular counters with
     // non-zero presence sentinels; the 4-bit cached role rides the top bits of the two count
-    // bytes (tier-3 role fallback). Full layout and rationale: docs/node_info_stores.md.
+    // bytes (tier-3 role fallback). Full layout and rationale:
+    // https://meshtastic.org/docs/development/reference/node-info-stores.
 #if _meshtastic_Config_DeviceConfig_Role_MAX > 15
 #warning "Device role enum max exceeds 15 - TMM 4-bit role cache (rate_count[7:6]/unknown_count[7:6]) will truncate new values"
 #endif
@@ -347,12 +349,14 @@ class TrafficManagementModule : public MeshModule, private concurrency::OSThread
 
     /// 60 s NodeInfo-cache maintenance under cacheLock: saturate the expired obsTick stamp (wrap-safety
     /// for the modular clock) and run the boot/hourly reconcile. Guarded by TMM_HAS_NODEINFO_CACHE alone
-    /// (never the unified cache size); see docs/node_info_stores.md "Tick clocks and wrap safety".
+    /// (never the unified cache size); see https://meshtastic.org/docs/development/reference/node-info-stores "Tick clocks and
+    /// wrap safety".
     void maintainNodeInfoCacheLocked();
 
     /// Anti-entropy under cacheLock: upsert hot-store + warm-tier records this cache lacks (never sets
     /// hasObserved - seeding is knowledge, not observation), and refresh isMember from both NodeDB
-    /// tiers. Cost/lag: docs/node_info_stores.md "Consistency with NodeDB (anti-entropy)".
+    /// tiers. Cost/lag: https://meshtastic.org/docs/development/reference/node-info-stores "Consistency with NodeDB
+    /// (anti-entropy)".
     void reconcileNodeInfoFromNodeDBLocked();
     /// Learn an observed NODEINFO frame into the cache (key hygiene + provenance rules apply).
     void cacheNodeInfoPacket(const meshtastic_MeshPacket &mp);
@@ -368,7 +372,8 @@ class TrafficManagementModule : public MeshModule, private concurrency::OSThread
 
     // Direct-response throttles bounding the reflector risk of spoofed replies: three fixed bounds
     // (per requester, per target, 1 s global airtime floor) via 8-slot LRU RAM tables, wrap-safe and
-    // PSRAM-agnostic. Design & rationale: docs/traffic_management_module.md "Throttling direct responses".
+    // PSRAM-agnostic. Design & rationale: https://meshtastic.org/docs/development/reference/traffic-management-internals
+    // "Throttling direct responses".
     static constexpr uint32_t kDirectResponsePerRequesterMs = 60'000UL;
     static constexpr uint32_t kDirectResponsePerTargetMs = 60'000UL;
     static constexpr uint32_t kDirectResponseGlobalMs = 1'000UL;