ci: FormatCheck gate + enable VersionCheck/Documentation w/ PR previews

[sotashimozono]

What

Brings ParallelManager's CI up to the infra standard (matching Pinax / DataVault), as one batch:

Change	Before	After
Format	FormatFix (auto-commits fixes)	FormatCheck — hard gate (format(".", overwrite=false), exit 1 on dirty, JuliaFormatter v2)
VersionCheck	disabled	enabled — every PR to main must bump Project.toml version
Documentation	disabled (docs didn't build)	enabled + push_preview PR previews; CleanupPreview.yml prunes previews/PR#<n> on PR close

Why Documentation was disabled — and the fix

The docs build failed (3 errors), so the workflow had been parked as .disabled. Fixed here:

1. checkdocs=:exports — the internal _run_pmap! / _run_sequential! / _run_one_with_lock! / _run_one_with_retry! helpers carry docstrings (good for source readers) but are not public API, so they shouldn't be required in the manual. :exports scopes the missing-docs check to exported symbols.
2. Added the 4 exported-but-undocumented symbols to api.md: run_loop!, verify_workers!, merge_and_save_manifest!, merge_event_logs — plus the top-level module docstring.
3. Manifest.jl: [ParamIO.canonical](@extref) → plain code span. @extref needs DocumenterInterLinks (not loaded), which surfaced as an "invalid local link" cross-reference error. Not worth wiring a cross-package inventory just to enable the build.

Docs now build green locally (julia --project=docs docs/make.jl → exit 0; only the expected "skipping deployment" notice off-CI).

Also

• .gitignore the build-time downloaded docs assets (favicon.ico, logo.png — fetched by make.jl at build; custom.css stays tracked).
• Bump 0.4.0 → 0.4.1. VersionCheck runs on its own introducing PR (for pull_request, GitHub uses the PR branch's workflow files), so the enabling PR must itself bump — mirroring Pinax's ci: enable VersionCheck workflow + bump version to 0.1.1 commit.

⚠️ Do not merge yet / coordination

• Hold for review (per the standing do-not-merge-until-confirmed instruction).
• Shares version 0.4.1 with the registration PR chore: General registration prep + CI standardization (0.4.1) #26 (chore/drop-sources-register, which drops [sources] + enables AutoRegister). Both branch off main, so whichever merges second needs a trivial rebase + re-bump — VersionCheck enforces this automatically. Suggested order: this CI PR first (no registration side-effects; AutoRegister stays .disabled here), then chore: General registration prep + CI standardization (0.4.1) #26 (rebases to 0.4.2, drops [sources], enables + triggers AutoRegister).

🤖 Generated with Claude Code

[github-actions]

📚 Docs preview: https://sotashimozono.github.io/ParallelManager.jl/previews/PR27/

(updates on each push to this PR)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
src/Manifest.jl	0.00% <ø> (ø)

🚀 New features to boost your workflow:

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

[sotashimozono]

Integrated into #26 (chore/drop-sources-register) per request — both targeted 0.4.1, so they're now one release: drop [sources] + enable AutoRegister + CI standardization (FormatCheck / VersionCheck / Documentation + previews) together. Closing this in favor of #26.