One chat-frame flow for live and history messages (#105) (#139)

Second slice of making MessageBusManagementThread testable. The CH (live)
and CR (history) chat-frame branches of processRXMessage23001 were near
copies; they are now one processChatFrame(fields, live), with behaviour
unchanged.

- InboundChatFrame, ChatRoute and classifyRoute: where a message belongs
  (public, to me, from me, between others), pure.
- ChatMessageEffects and decideChatFrameEffects: what a message triggers
  (sounds, //BELL, //VER reply, auto-answer, directional tick, in-angle
  flag, DX cluster spot), pure. History frames trigger nothing but the flag.
- The four live/history differences are kept on purpose: frequency
  detection before routing (live) or after publishing (history), effects
  for messages to me, tick and spot between others, AirScout info on the
  SERVER sender.
- MessageBusManagementThreadChatFrameTest pins both branches through the
  real thread, including the frequency order on directed frames and the
  spot entry; ChatFrameDecisionTest covers the pure functions.
- Spec: docs/superpowers/specs/2026-10-16-message-bus-second-slice-design.md

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

docs/PROJECT_CONTEXT.md

@@ -365,6 +365,7 @@ section records only the durable architecture and operational boundaries.
 - Keep canonical worker-thread domain state separate from the row lists the user interface draws from.
 - The station map is a Compose canvas that fetches its own tiles. The JavaFX WebView, the bundled Leaflet resources, the CSS-3D-transform workaround and the `TileProxyServer` were removed with JavaFX; offline DEM, terrain packages and the profile cache are unaffected and must stay that way.
 - Deliberate test data, comments and Easter eggs are preserved unless explicitly changed.
+- Chat frames (issue #105, second slice): CH (live) and CR (history) go through one `MessageBusManagementThread.processChatFrame(fields, live)`. `classifyRoute` and `decideChatFrameEffects` are pure; history frames never play sounds, answer or spot, and keep their frequency extraction after publishing. Known oddities kept on purpose: TO_ME is case-sensitive, FROM_ME case-insensitive; the CR SERVER sender has no AirScout info.
 
 ## Planned Technical Direction