Document the capability model as ADR 0001

[tony]

Summary

• Add a numbered architecture decision collection for contributor-facing, long-lived decisions.
• Define ADR 0001 as the shared capability contract for tmux MCP implementations, based on the source decision in #127.
• Specify socket-scoped object selection, independent direct-capability properties, startup tool-surface resolution, whole-call MCP annotations, the host-command boundary, and disclosure obligations.
• Separate normative BCP 14 requirements from informative rationale, consequences, rejected alternatives, security considerations, and reconsideration criteria.
• State ambient execution, aggregate authority, shared-socket ownership, untrusted output, bounded matching, and redaction limits without claiming containment.

Verification

$ uv run ruff format . --check

$ uv run ruff check .

$ uv run mypy .

$ uv run pytest -n 0 --reruns 0

$ just build-docs

Test plan

• Publish the ADR collection from the Project page and retain the source-decision provenance.
• Give ADR 0001 a self-contained abstract, explicit conformance target, controlled terminology, and proposition-style CM-* headings.
• Apply named includes and exclusions to the effective surface, including aggregate authority.
• Distinguish direct process reach from ambient tmux execution and transport subprocesses.
• Qualify shared-socket shutdown against the tmux 3.2a exit-empty and exit-unattached behavior.
• Build the complete Sphinx site with warnings treated as errors.
• Verify every code citation uses a tag-pinned GitHub URL with line anchors and returns HTTP 200.
• Run the full formatting, lint, typing, and serial test gates.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.91%. Comparing base (d69ec57) to head (2af0b0c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #130   +/-   ##
=======================================
  Coverage   86.91%   86.91%           
=======================================
  Files          46       46           
  Lines        3874     3874           
  Branches      583      583           
=======================================
  Hits         3367     3367           
  Misses        355      355           
  Partials      152      152           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.