TMM & Warmstore key source naming (#11119)

* one becomes two

* warmstore clarify

* Address PR review: key-provenance terminology consistency

- Log line now says "not key-proven" (gate is XEdDSA OR manual, not just signer)
- Rename markKeySignerProvenForTest -> markKeyXeddsaSignedForTest (sets only the XEdDSA bit)
- Docs + test comments: "signer bit" -> "XEdDSA-signed bit"

clod helped too

* Rename signer-proven -> key-proven for broadened provenance predicate

Address PR #11119 review: the copyPublicKey()/copyUser() out-parameter and
the cache-path replay gate now report entry->keyProven() (XEdDSA-signed OR
manually verified), so the "signerProven" name and "signer-proven" comments
were misleading. Rename the public out-param to keyProven, the local
cachedKeySignerProven to cachedKeyProven, and update coupled callers, log
strings, docs headings, and comments to say "key-proven".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* nitpicks

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

src/mesh/Router.cpp

@@ -838,7 +838,7 @@ DecodeState perhapsDecode(meshtastic_MeshPacket *p)
         // Resolve the sender's key only for actual PKI-decrypt candidates, not every encrypted channel
         // packet: copyPublicKeyForDecrypt() can fall through to a linear scan of TrafficManagement's large
         // NodeInfo cache. It returns authoritative keys (hot/warm), or a cold-tier cache key only when it is
-        // signer-proven - an unverified TOFU cache key must not back authenticated (pki_encrypted, p->from)
+        // key-proven - an unverified TOFU cache key must not back authenticated (pki_encrypted, p->from)
         // DM attribution.
         meshtastic_NodeInfoLite_public_key_t remotePublic = {0, {0}};
         bool haveRemoteKey = nodeDB->copyPublicKeyForDecrypt(p->from, remotePublic);