[tractorjuice]

Adds a Registering a new community overlay section to CONTRIBUTING.md, covering the integration points a new plugins/arckit-<name>/ directory must hit.

Raised by @umag while contributing the Netherlands overlay (#739) — both points were found by running the tooling, not by reading the contributing guide.

The two silent failures

scripts/converter.py → PLUGIN_SOURCES. A missing entry produces zero files for the overlay across all seven non-Claude extensions, and the converter still exits 0 with a success summary. Nothing looks wrong. This cost arckit-uk-finance four releases (v5.3.0 → v5.6.0) of entirely missing extension output. The section also names the two deliberate exclusions — arckit-fde (Claude-only tooling) and arckit-uk-gcloud (proprietary, must not leak into the MIT extension repos) — so nobody adds them while "fixing" the list.

Both marketplace manifests. There are two, with different source shapes, tabulated in the section because the asymmetry is the part that catches people:

Manifest	Source shape
.claude-plugin/marketplace.json	flat — ./plugins/arckit-nl
plugins/arckit-claude/.claude-plugin/marketplace.json	nested — ./plugins/nl

tests/plugin/test_release_process.py compares both against EXPECTED_CLAUDE_MARKETPLACE_SOURCES, so updating one but not the other fails CI — but omitting all three passes silently, since the length and set assertions still agree.

Slightly wider than the two points

One further subsection lists the rest of the same registration act: sync-claude-plugin-layout.py (PLUGIN_LAYOUT), push-extensions.sh (CLAUDE_PLUGIN_LAYOUT), the four test enumeration lists, and sync-shared-assets.py (SYNC_EXEMPT_PLUGINS).

Rationale: a contributor who fixes only the two named points still ships a broken overlay, and the test lists are exactly what turns the converter omission from silent into loud — .github/workflows/python-tests.yml regenerates the extensions and then runs the full suite, so an overlay present in PLUGIN_COMMAND_DIRS but absent from PLUGIN_SOURCES fails CI. That is worth stating, because it makes adding the test entries load-bearing rather than bookkeeping.

Happy to trim it back to just the two if you would rather keep the section tight.

Verification

All claims checked against main rather than carried over from notes — one such note was stale and would have been wrong: tests/plugin/ is now in CI unfiltered since #720, so the section documents the test lists as a working guard, not a gap.

npx markdownlint-cli2 CONTRIBUTING.md    0 issues
scripts/check_references.py              791 files, no broken references
scripts/check-guide-site-links.py        238 guides, all reachable

Docs-only change; no commands, templates, or config touched.

🤖 Generated with Claude Code

https://claude.ai/code/session_01VKbHCujejpxkgvh47BndDE