docs: update README and AGENTS.md for session persistence, characteristics, track endpoints

- Document session persistence model (split metadata/frames files, lazy load)
- Add characteristics API endpoints and response examples
- Add track API endpoints to endpoint table
- Fix use case name track_map → track_mapping
- Update architecture with characteristics.rs and track_model.rs
- Update test count to 33
- Rewrite AGENTS.md: accurate ports, persistence paths, tech stack

AGENTS.md

@@ -0,0 +1,54 @@
+# AGENTS.md — rusty-telemetry Project Context
+
+## Mandatory Reference
+
+**Before starting any work on this project, always read the Joplin note that contains the full project plan and architecture.**
+
+- **Joplin Note ID**: `6c0dcb2a567348fd9796f50c790082e4`
+- **Title**: "Sim Racing Telemetry Analysis Platform — Project Plan"
+- **Tags**: sim-racing, lua, telemetry, rust, project-plan, assetto-corsa
+
+Use the `joplin_get_note` tool with note ID `6c0dcb2a567348fd9796f50c790082e4` to retrieve the full project plan.
+
+## Project Overview
+
+`rusty-telemetry` is a Rust-based multi-port UDP telemetry listener and analysis platform for sim racing. It receives telemetry from Assetto Corsa (KSUDP + Telemetry Tool) and Project CARS 1 & 2, provides a terminal dashboard (ratatui), and exposes a REST API for session management, analysis, and car characteristics aggregation.
+
+## Companion Repository
+
+| Field | Value |
+|-------|-------|
+| **Repo** | `racecraft` |
+| **Path** | `~/WebstormProjects/racecraft` |
+| **Language** | TypeScript (Vue 3) |
+| **Purpose** | Web client — live telemetry, session UI, charts, track maps |
+
+## Tech Stack
+
+- Rust (edition 2021)
+- Tokio (async runtime)
+- Axum 0.8 (REST API)
+- Ratatui (terminal UI)
+- Serde (JSON serialization)
+
+## Key Ports
+
+| Port  | Feed Name         | Source                        | Format  |
+|-------|-------------------|-------------------------------|---------|
+| 9996  | ksudp             | AC built-in engine             | Binary (3-phase handshake, RTCarInfo) |
+| 10101 | telemetry_tool    | Telemetry Tool Python plugin   | Binary (per-driver structs, ~60 Hz) |
+| 5606  | pcars             | Project CARS 1 & 2             | Binary (V1 1367B / V2 559B, auto-detected) |
+| 8080  | REST API          | Axum HTTP server               | JSON |
+
+## Data Persistence
+
+- **Recordings**: `./data/<uuid>/` — manifest.json + per-feed JSONL files (written on shutdown)
+- **Sessions**: `./data/sessions/<id>.json` (metadata + analysis) + `<id>.frames.json` (frames, lazy-loaded)
+- **Track Models**: stored in session analysis results, served via `/api/tracks`
+
+## Commands
+
+```bash
+cargo run --release    # Start server + TUI
+cargo test             # Run 33 unit tests
+```