Runtime proxy spawn: Stage 3 PlaceAtMe

Promote a single runtime-spawned proxy as the preferred active remote-player representation (Stage 3 / 3.7) while preserving the placed reference as a fallback. Updates include: detailed architecture and dev-log additions describing staged diagnostics (3.1–3.7), PlaceAtMe-backed spawn candidate isolation/settle, vanilla/Codsworth diagnostics, console PlaceAtMe testing, near-player visibility holds, and PASS/PARTIAL/FAIL diagnostic outcomes.

Code changes (plugin/include & plugin/src): adjust header comment and implement numerous runtime proxy features and diagnostics: new constants, enums, structs, state variables, logging helpers, position/distance helpers, absolute FormID lookup, runtime actor base selection (custom vs vanilla), PlaceAtMe-backed spawn state machine, debug placement/hold timing, candidate snapshot/isolation, promotion to active runtime proxy, and many throttled/logged diagnostics. The placed CK reference remains the fallback if runtime spawn/validation fails. Docs changed: docs/architecture.md and docs/dev-log.md updated to describe the new Stage 3 behavior and testing notes.

Files changed: docs/architecture.md, docs/dev-log.md, plugin/include/F4TProxyActorController.h, plugin/src/F4TProxyActorController.cpp.

Behavioral notes: single-proxy only (Stage 4 mapping deferred), extensive diagnostic logging added, and in-game validation/testing remains pending.

plugin/include/F4TProxyActorController.h

@@ -2,7 +2,7 @@
 
 namespace F4T::ProxyActorController
 {
-	// Game-thread-only actor controller for proxy diagnostics and the active placed proxy test actor.
+	// Game-thread-only actor controller for the single active runtime proxy and placed fallback.
 	// Networking threads must only update plain remote-player state.
 	void Update();