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>

arautopilot/tests/test_project_config.py

@@ -0,0 +1,73 @@
+"""Tests for ``arautopilot.core.project_config``."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+from pydantic import ValidationError
+
+from arautopilot.core import ProjectConfig
+
+
+def test_project_has_required_fields(basic_project: ProjectConfig) -> None:
+    assert basic_project.project_id
+    assert basic_project.client_name
+    assert basic_project.project_name
+    assert basic_project.vessel is not None
+    assert basic_project.schema_version == "0.1.0"
+
+
+def test_to_dict_is_json_safe(basic_project: ProjectConfig) -> None:
+    import json
+    d = basic_project.to_dict()
+    # json.dumps would raise on raw datetimes; model_dump(mode="json") avoids that.
+    encoded = json.dumps(d)
+    assert "project_id" in encoded
+
+
+def test_round_trip_json(basic_project: ProjectConfig) -> None:
+    text = basic_project.to_json()
+    rebuilt = ProjectConfig.from_json(text)
+    assert rebuilt == basic_project
+
+
+def test_round_trip_yaml(basic_project: ProjectConfig) -> None:
+    text = basic_project.to_yaml()
+    rebuilt = ProjectConfig.from_yaml(text)
+    assert rebuilt == basic_project
+
+
+def test_save_and_load_yaml(tmp_path: Path, basic_project: ProjectConfig) -> None:
+    out = tmp_path / "project.yaml"
+    basic_project.save_yaml(out)
+    rebuilt = ProjectConfig.load(out)
+    assert rebuilt == basic_project
+
+
+def test_save_and_load_json(tmp_path: Path, basic_project: ProjectConfig) -> None:
+    out = tmp_path / "project.json"
+    basic_project.save_json(out)
+    rebuilt = ProjectConfig.load(out)
+    assert rebuilt == basic_project
+
+
+def test_load_rejects_unknown_extension(tmp_path: Path, basic_project: ProjectConfig) -> None:
+    bogus = tmp_path / "project.toml"
+    bogus.write_text("# nothing", encoding="utf-8")
+    with pytest.raises(ValueError):
+        ProjectConfig.load(bogus)
+
+
+def test_rejects_unknown_top_level_field(basic_project: ProjectConfig) -> None:
+    d = basic_project.to_dict()
+    d["surprise"] = "value"
+    with pytest.raises(ValidationError):
+        ProjectConfig.from_dict(d)
+
+
+def test_touch_updates_modified_at(basic_project: ProjectConfig) -> None:
+    original = basic_project.modified_at
+    bumped = basic_project.touch()
+    assert bumped.modified_at >= original
+    assert bumped.project_id == basic_project.project_id