Fix reference sync, slugs, and linting issues (CX-3425)

[jesseyowell]

Fixes the follow-up issues from CX-3425.

Update: main removed the numbering.js validator entirely (the -N auto-renamer) to fix a duplicate-pages bug. This branch has merged that change and drops CX-3425 item 2 (the -1 renamer + redirect file) accordingly — the auto-rename approach is gone, so its redirect enhancement no longer applies. Item 2 should be revisited as a redirect-only approach in a follow-up, coordinated with @minhthanhdang. The remaining four items are unaffected.

What changed

1. Reference pages are OAS-owned. oas:sync no longer writes or updates title/excerpt on api-backed reference pages (generated pages carry only api.file + api.operationId); the frontmatter linter no longer requires title on reference pages that declare api.file; and the title/excerpt "out of sync" checks were removed. This clears the must have required property 'title' and Out of sync: title…/excerpt… false positives. Existing title/excerpt are left untouched (non-destructive).
2. Cross-section duplicate slugs allowed. Duplicate-slug detection is now scoped per top-level section, so the same slug in docs/ and reference/ is no longer flagged.
3. Unknown components are warnings. Components not built-in or in local custom_blocks/ (e.g. <ClosedBeta> global/Enterprise blocks) are now warnings, not errors, so they don't fail CI.
4. Stale _order.yaml entries flagged. Entries listed in _order.yaml with no matching file/folder — and index entries — are now flagged (warning) and removable with --fix, across docs/, reference/, recipes/, and custom_pages/. (Implemented as a single per-directory pass that diffs the on-disk slug set against the _order.yaml entries.)

(Dropped: item 2, the -1 renamer/redirects — see the update note above.)

Tests

Adds a node:test suite under test/ (the repo previously had none): 17 tests, all passing (npm test). Covers each changed validator plus edge cases (cross-section duplicates allowed, unknown component is a warning, --fix add/remove paths, a folder entry with no markdown children is not flagged stale).

End-to-end verification

Ran lint on the Lightcast reference project (~1,111 reference pages) with main vs. this branch:

Rule / severity	Before	After
frontmatter required-title errors	327	0	✅ item 1
oas-reference "Out of sync" title/excerpt	723	0	✅ item 1
duplicates cross-section false positives	3	1	✅ item 2 (now item numbering shifted)
ordering stale _order.yaml entries	0	2 (newly caught)	✅ item 4
Total errors	339	10

~1,050 false-positive findings eliminated on reference content that OAS now owns. The 10 remaining errors are 1 real within-reference/ duplicate + 9 real broken links — genuine pre-existing issues, not regressions, so lint still correctly exits 1. Verification was read-only; no --fix against the cloned data.

Notes

• The docs: commits are the design spec and implementation plan under docs/superpowers/ — planning artifacts, not product code.
• Version bumped to 0.0.29.
• Includes a merge of main (which removed the numbering.js validator).

🤖 Generated with Claude Code