feedback: game-to-cockpit endpoint (pipe/UDP lamps+plasma), rumble lamp flash

Phase 9: FeedbackPipeServer (\\.\pipe\riojoy-feedback) + loopback UDP share a
forgiving text line protocol into FeedbackRouter; CoalescingLampScheduler rate-
governs the 9600-baud link; plasma finally wired into activation (greeting,
teardown blank, PlasmaDisplay write lock); ViGEm FeedbackReceived drives
RumbleLampAdapter. Per-profile Feedback config, docs/FEEDBACK.md, 425 tests.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/PLAN.md

@@ -183,8 +183,11 @@ Implemented in `src/RioJoy.Core/Calibration` + `Plasma` (105 xUnit tests total):
 - `PlasmaCommands` ports the `CPlasma` ESC command set (clear/cursor/font/attr/box
   draw+fill/text) + `GetFontSize` + the `PlasmaPosText` auto-fit/centering;
   `PlasmaDisplay` writes them over the secondary COM transport.
-- ⏳ **Remaining:** hardware verification of axis feel + plasma output; the
-  game-specific `PlasmaScoreDraw` layout is profile content (Phase 5/7).
+- ⏳ **Remaining:** hardware verification of axis feel + plasma output. Runtime
+  plasma wiring (secondary port open, greeting, teardown) landed in **Phase 9**;
+  the legacy game-specific `PlasmaScoreDraw` layout is superseded by the Phase 9
+  feedback endpoint (external clients draw score/status content —
+  [`docs/FEEDBACK.md`](FEEDBACK.md)).
 
 ### Phase 5 — Tray app + profiles — code-complete ✅
 Core logic in `src/RioJoy.Core/Profiles` + `RioRuntime`; UI/OS in `src/RioJoy.Tray`
@@ -431,6 +434,58 @@ XP consumes pre-rendered wallpapers.
      computers, adds shortcuts); the single dist zip carries everything
      needed for both XP and 10/11, including offline redistributables.
 
+### Phase 9 — Game feedback (game → cockpit) — code-complete ✅
+Inbound feedback endpoint + plasma runtime wiring + rumble→lamp mapping, in
+`src/RioJoy.Core/Feedback` (425 xUnit tests total across the suite); protocol
+spec + client snippets in [`docs/FEEDBACK.md`](FEEDBACK.md). Delivers the
+§Profiles promises "Lamp behavior" and "Plasma/VFD content (or 'off')".
+- **Endpoint**: `FeedbackPipeServer` serves `\\.\pipe\riojoy-feedback`
+  (read-only — no replies ever, which sidesteps the 0-buffer pipe write
+  deadlock class; ≤4 concurrent clients; reconnect forever; vRIO's
+  `VRioPipeService` server pattern incl. the poke-connect stop) and
+  `FeedbackUdpListener` binds loopback-only UDP (off by default,
+  `AppConfig.Feedback.UdpPort` — the transport sim export scripts speak
+  natively). One shared text line protocol: `FeedbackLineParser` +
+  `FeedbackLineBuffer` (Latin-1, LF/CRLF, forgiving — malformed lines drop and
+  log, never the connection). `FeedbackService` façades the lot; it lives in
+  `RioCoordinator` for the **app lifetime**, so clients keep their connection
+  across profile switches and dormancy — only command *application* is gated.
+- **Rate governor**: `CoalescingLampScheduler` — per-address desired/last-sent
+  shadow state, at most one *changed* lamp per 25 ms tick, round-robin. All
+  feedback lamp traffic (pipe/UDP and rumble) posts here; nothing feedback-side
+  calls `ILampSink` directly, because every lamp command crosses the link's
+  stop-and-wait command gate (~150 ms worst case) shared with the ~55 ms
+  analog poll.
+- **Routing/precedence**: `FeedbackRouter` — per-profile gating
+  (`RioProfile.Feedback`, null = feedback off; `AllowLampCommands`/
+  `AllowPlasmaText`), profile-owned lamps (`HasLamp`) protected from
+  press/release fights (dropped, logged once per address per attach), plasma
+  writes single-flight with a latest-pending-wins slot.
+- **Plasma wired at last** (closes the Phase 4 ⏳ wiring): `RioCoordinator.
+  Activate` opens `PlasmaComPort ?? DefaultPlasmaComPort` via the transport
+  factory (`pipe:` endpoints work for benchless testing; `"off"`/empty skips;
+  failure becomes a status suffix and never breaks activation), shows
+  `PlasmaGreeting` auto-centered, blanks + releases the port on teardown (the
+  native games open this port too). `PlasmaDisplay` gained its missing write
+  lock — `PosTextAsync` is five transport writes, and concurrent callers used
+  to interleave ESC fragments (`PlasmaDisplayTests` pins both the sequence and
+  the no-interleave guarantee).
+- **Rumble → lamps** (net48 only): `ViGEmJoystickSink.RumbleChanged` (plain
+  byte delegate over ViGEm's `FeedbackReceived`; fires on a ViGEm-owned
+  thread) → `RumbleLampAdapter`: off below `Threshold`, then slow/med/fast
+  thirds at full brightness per motor, posting only state **changes** so
+  XInput's identical-value spam costs nothing — the board sustains the blink
+  from the state byte. Works with unmodified games that set XInput vibration.
+- Config: `FeedbackEndpointConfig` (app-wide) + `ProfileFeedbackConfig` /
+  `RumbleLampConfig` (per-profile); nullable sections = off/defaults, keeping
+  pre-Phase-9 JSON byte-compatible (round-trip, unset-stays-null, and
+  shipped-profile cases in `ConfigStoreTests`).
+- ⏳ **Remaining:** on-cabinet verification (real lamps + plasma glass, link
+  feel under game load); timed flash-then-restore effects (the scheduler's
+  shadow state is the designed hook); editor UI for the per-profile feedback
+  settings (JSON-only today); shipped client examples (SimHub plugin / DCS
+  export script) beyond the FEEDBACK.md snippets.
+
 ---
 
 ## Open items / risks