sprint-0: foundations -- data model, seed library, tests, demo

Initial commit. Delivers what the brief calls 'Sprint 0 - Foundations'
(see docs/AR_Autopilot_brief.md section 12):

- Complete repository structure (arautopilot package + firmware, display,
  installer, tools placeholders + docs).
- Core data model (Pydantic v2): modes, alarms, actuator config, PID
  config + gain scheduling, vessel config, knob state machine, project
  config with YAML/JSON serialisation.
- Seed library: 2 actuator profiles (hydraulic & electric DC reversible)
  and 2 default tunings (yacht motor planeo 30 m and 40 m). Conservative
  literature values, NOT the integrator's production tuning IP.
- Firmware skeleton: only src/hal/pinout.h with the 21 I/O contract for
  the AR-NMEA-IO v1.0 board. No drivers, no main loop.
- Studio stubs (real PySide6 app starts in Sprint 4).
- pytest suite (80 tests, all green): modes, alarms, actuator, PID
  (incl. gain interpolation and the +/-50% adaptive bound from brief
  section 6), vessel, knob state, project config, library loader,
  end-to-end roundtrip.
- examples/sprint0_demo.py - the acceptance demo from the brief.

Acceptance criteria met:
- pytest green (80/80)
- demo creates, saves (YAML + JSON), reloads, and verifies a full
  ProjectConfig using the seed library
- repository ready for tag `sprint-0-approved`

See CHANGELOG.md for the detailed scope.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -0,0 +1,44 @@
+# Changelog
+
+All notable changes to AR-Autopilot will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+---
+
+## [Unreleased]
+
+## [0.1.0] — Sprint 0 — Foundations — 2026-05-17
+
+### Added
+
+- Repository structure following the layout defined in the project brief (section 11)
+- Python package skeleton `arautopilot` with submodules:
+  - `core/` — data model (Pydantic v2): modes, alarms, actuator config, PID config,
+    vessel config, knob state, project config, IDs
+  - `library/` — curated seed: 2 actuator profiles (hydraulic reversible,
+    electric DC reversible) and 2 default tunings (yacht motor planeo 30 m, 40 m)
+  - `studio/` — empty stubs for Sprint 4
+  - `tests/` — pytest suite covering the core data model
+- Firmware skeleton: `firmware/ar_autopilot_v1/src/hal/pinout.h` only —
+  21 I/O assignment for the AR-NMEA-IO v1.0 board, no functional code yet
+- Build configuration:
+  - `pyproject.toml` with Pydantic v2, PyYAML, python-dateutil
+  - Dev dependencies: pytest, pytest-cov, ruff, mypy
+  - Ruff + mypy strict configuration
+- `examples/sprint0_demo.py` — end-to-end project creation, save, and reload
+- Documentation moved/created:
+  - `docs/AR_Autopilot_brief.md` — full project brief
+  - `docs/architecture.md` — one-page architecture overview
+- `LICENSE.txt` — Proprietary, all rights reserved
+- `.gitignore` covering Python, Flutter, PlatformIO, IDEs, Windows artifacts
+
+### Notes
+
+- **No functional firmware**, Studio GUI, or display in this sprint — those
+  start in Sprint 1, 4, and 4 respectively.
+- The seed PID tunings are **conservative starting values** drawn from
+  classical marine control literature (Fossen, Perez). They are explicitly
+  **not** the integrator's affinated production values, which remain IP.
+- Python ≥3.11 required.