Add optional ACP coding-agent package

[scald]

Summary

• add an optional nooa-acp distribution that serves a NOOA coding agent over ACP on stdin/stdout
• translate agent messages, tool progress, usage, resource links, cancellation, and stdio MCP servers into ACP protocol behavior
• register both the standalone nooa-acp executable and the nooa acp plugin command
• include the package in workspace, CI, release, smoke-test, and third-party notice flows

Verification

• uv run pytest -q -m "not integration and not stress": 6526 passed, 6 skipped, 282 deselected
• uv run ruff check .
• uv run ruff format --check .
• SPDX/license checks and uv lock --check
• built all five wheels and source distributions with --no-sources; all passed twine check
• installed all five wheels in a clean Python 3.12 environment and verified imports, nooa --help, and nooa-acp --help
• independent pre-landing and Codex reviews: no unresolved findings

Release Setup

Before first publication, maintainers must create the pypi-nooa-acp and testpypi-nooa-acp GitHub environments and matching trusted publishers.

Closes #76

[alessiodevoto]

@dcoapp recheck

[furgalep]

Thanks @scald for this PR. I'm looking at bringing our coding agent terminal ui over and supporting ACP at the same time. I'll keep you posted.

[furgalep]

Superseded by #143, which carries your four commits from this branch — feat: add ACP coding agent package, feat(mcp): add async stdio tool factory, and the two model-default fixes — rebased onto current main with authorship and sign-offs intact.

Both add packages/nooa-acp, so they cannot merge independently. #143 builds the durable-session, workspace-skill and MCP work on top, and has been through a review pass plus live testing against Zed.

Flagging rather than closing, since it is your PR — happy for you to close it, or say the word and I will.