docs: update README and AGENTS.md for characteristics, tracks, endpoint changes

- Add Car Characteristics and Track Mapping feature sections
- Update project structure (8 routes, tracks store, new views)
- Update API contract (23 endpoints, add characteristics/tracks/build-track-model)
- Add Features and State Management sections to AGENTS.md

AGENTS.md

@@ -46,7 +46,24 @@ Use the `joplin_get_note` tool with note ID `6c0dcb2a567348fd9796f50c790082e4` t
 
 ## API Communication
 
-Racecraft communicates exclusively with the rusty-telemetry REST API. In development, Vite proxies `/api/*` to `http://127.0.0.1:8080`. See the rusty-telemetry README for full endpoint documentation.
+Racecraft communicates exclusively with the rusty-telemetry REST API (23 endpoints). In development, Vite proxies `/api/*` to `http://127.0.0.1:8080`. See the rusty-telemetry README for full endpoint documentation.
+
+## Features
+
+- **Dashboard** — system status, live feed cards, recent sessions
+- **Live Telemetry** — real-time gauges (speed, RPM, gear, inputs), per-feed status
+- **Sessions** — create/complete/reopen sessions, start/stop/delete runs, view analysis
+- **Shift Points** — gear RPM range charts, shift event timeline, recommended shift RPM
+- **Car Characteristics** — aggregated shift-point profiles per car across all sessions
+- **Track Mapping** — canvas-rendered track boundaries, persistent track models
+
+## State Management (Pinia Stores)
+
+| Store | Purpose |
+|-------|---------|
+| `stores/telemetry.ts` | Live telemetry polling + derived status |
+| `stores/sessions.ts` | Session CRUD, run management, analysis retrieval |
+| `stores/tracks.ts` | Track model list + detail |
 
 ## Commands