feat(cli): detect project roots across ecosystems, not just Node

[ophiocus]

Closes #199 — and big thanks to @AndreyGritsa, whose nine-Poetry-roots-plus-Next.js layout from the issue thread is now a test case in this PR. That fixture reshaped the design: the fix isn't an adapter table alone, it's multi-root, multi-ecosystem detection, because a repository with no root package.json and independent Python packages beside a frontend was previously invisible to init.

What changed

packages/cli/src/detect.mjs:

• Ecosystem adapter table — Node, Python (Poetry/uv/PDM/Hatch/pip), PHP (Composer), Go, Ruby, Rust, Java (Maven/Gradle). Same shape as detectDeploymentProvider: adding an ecosystem is one entry, not a branch. Each adapter only proposes tools the project actually configures (ruff/mypy/pytest from pyproject.toml, phpunit/pest from the files present, and so on).
• Multi-root walk (depth ≤ 3) — every project root is discovered and kept. Checks are unioned and root-scoped — (cd scraper && poetry run pytest) — so a change anywhere in the repository has a gate. Provisioning is per root (poetry install in the touched package), not one repo-wide install, which a layout like Andrey's can't express.
• Workspace absorption — pnpm/npm/Cargo workspace members (and packages nested below them, e.g. runner/agent-clis) are absorbed into their workspace root, whose scripts already fan out to them. This is what keeps existing Node repositories detecting identically to before.
• Fixture/sample directories are never roots — test/, fixtures/, samples/, examples/ hold manifests on purpose; proposing their checks as repository defaults would be noise (found by running the new detection against claude-dev-kit, where samples/php volunteered its phpunit as a repo default).
• test:run fallback when test is absent — the watch-free vitest convention, and literally the script name in the frontend from the issue thread.

detect() also returns two new advisory fields, ecosystems and roots (path/ecosystem/manager), which init can surface in its summary; existing consumers are untouched.

apps/docs/docs/faq.md: the "Does this work for non-Node projects?" answer now describes what detection actually does instead of promising only a marked slot.

How it's verified

• New packages/cli/test/detect.test.mjs, 5 cases: single-root npm unchanged; pnpm workspace absorption incl. the nested-member case; the polyglot no-root-manifest monorepo from Stack detection covers only the Node ecosystem — every other stack starts on an empty job site #199; PHP + Go roots with migration discovery; fixture/sample dirs never become roots.
• Full CLI suite: 103 tests, 0 failures (98 before this PR — the five are new).
• Backward-compatibility proof, not just tests: ran main's detect() and this branch's detect() against facility's own checkout — every shared output field is identical, byte for byte. CDK's real tree confirms the fixture-skip.

@AndreyGritsa — your offer to validate against the real monorepo stands very welcome: this should now discover all nine Poetry roots plus frontend/, propose poetry install per touched package, and union poetry run pytest with npm run test:run. I'd love to hear where it guesses wrong.