fix(lint): give broken-link stubs the type of the folder they land in (#733)

[dajiaohuang]

Refs #733 — addresses the first half of the report (the type: query stubs).

Wiki Lint's "Fix broken link" keeps the directory of the link it replaces but
hard-coded type: query on the stub. Only wiki/queries/ made that true.
Everywhere else it did two kinds of damage at once:

• src/lib/wiki-graph.ts:242 drops every node whose type is query
  (HIDDEN_TYPES), so the new page and every link pointing at it vanished
  from the graph. That is also what drove the inflated isolated-page count in
  Insights.
• The project's own schema routing rejected the file on the next ingest — a page
  under wiki/concepts/ must carry type: concept. The app was refusing
  content it had written itself.

inferStubType() now derives the type from the stub's destination directory.

The project's schema.md is consulted first, and that ordering is the part
worth reviewing. The report suggested inferWikiTypeFromPath, but that map is
built-in only: for the custom folders in the report's own measurements
(playbooks/, standards/) it returns the plural directory name, which would
still fail validateWikiPageRouting's exact match and leave the page dropped
on the next ingest. The schema table is what routing actually validates
against, so it wins. With no schema to consult, inferWikiTypeFromPath
(previously used only for UI labels) supplies the type; query stays the last
resort.

The schema is read after the exists-check, so the common "stub already there"
path does no extra I/O.

Not addressed

The second half of the report: makeQueryFileName always appending
-YYYY-MM-DD-HHMMSS, so a page created from a review suggestion is never
recognised by sweepResolvedReviews's exact-name match and the suggestion
returns on the next sweep. Fixing it changes the filename policy for every
"Save to Wiki" write, well beyond this stub path. I left it out deliberately
rather than smuggling a broad filename change into a lint fix — happy to do it
as a separate PR, or to fold it in here if you would rather review them
together.

Verification

10 new tests in src/lib/lint-fixes.test.ts (8 of the 18 fail against the
unfixed source), including one that feeds the generated frontmatter through
validateWikiPageRouting and asserts it is accepted — the exact check that
used to reject it.

• npx vitest run src/lib/lint-fixes.test.ts → 18 passed
• npm run test:mocks → 133 files / 1909 tests passed (no regressions)
• npx tsc --build → clean
• npx vite build → succeeds

Stubs are identified downstream by tags: [stub, lint], not by their type, and
ensureBrokenLinkStub has only one production caller (lint-view.tsx), so
nothing keys off the old query value. I have not run this against a real
2,900-file wiki; the report's reproduction is the basis for the test fixtures.

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