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>

README.md

@@ -20,8 +20,9 @@ Red Planet — talk to the RIO directly and do not use this app.)
 | [`driver/`](driver/) | `RioGamepad` virtual HID driver (KMDF + VHF) — replaces vJoy |
 | [`tools/RioJoySmokeTest`](tools/RioJoySmokeTest/) | On-cabinet end-to-end check of the feeder → driver path |
 | [`tools/XcfRegionExtract`](tools/XcfRegionExtract/) | Extracts cockpit label regions from `riojoy.xcf` → `regions.json` |
-| [`docs/PLAN.md`](docs/PLAN.md) | Full modernization plan (7 phases) |
+| [`docs/PLAN.md`](docs/PLAN.md) | Full modernization plan |
 | [`docs/PROTOCOL.md`](docs/PROTOCOL.md) | RIO wire format + `iRIO` input-map reference |
+| [`docs/FEEDBACK.md`](docs/FEEDBACK.md) | Game→cockpit feedback endpoint (lamps + plasma over pipe/UDP, rumble) |
 | _RIO board hardware & firmware_ | Moved to the [TeslaRel410 `restoration/`](https://gitea.mysticmachines.com/VWE/TeslaRel410/src/branch/main/restoration) archive — board photos, schematics, GAL decode (`restoration/rio-hardware`) and the RIO 4.3 board firmware (`restoration/rio-firmware`) |
 | [`docs/reference/`](docs/reference/) | Cockpit overlay art & the legacy labeling pipeline |
 | [`legacy/`](legacy/) | Original C++/vJoy implementation, kept as reference |
@@ -41,7 +42,9 @@ dotnet test RioJoy.sln
 
 ## Status
 
-Phases 1–5 are implemented and tested (241 unit tests). The `RioGamepad` virtual
+Phases 1–5 and 9 are implemented and tested (425 unit tests). Games (or sim
+export scripts) can drive the cockpit lamps and plasma display back through the
+running app — see [`docs/FEEDBACK.md`](docs/FEEDBACK.md). The `RioGamepad` virtual
 HID driver is built (KMDF + VHF), **test-signed, installed, and verified**: it
 enumerates in `joy.cpl`, and the C# HID feeder (`DeviceIoControl` →
 `RioGamepad.sys`) drives its axes, buttons, and hat end-to-end (see