wiki lint: orphan pages, stale pages, dead links, uncited sections (roadmap 1.4)

[joaovictor91123]

What you're trying to do

ROADMAP.md's 1.4 milestone calls for "wiki lint: orphan pages, stale pages,
dead links, uncited sections" — none of the four exist today. Once a page
is approved, nothing re-checks it: a [[wikilink]] whose target is later
archived, a page nothing else links to, a page not touched in a year, or a
hand-edited page whose citation coverage eroded after approval all surface
nowhere. health.lint()/vouch lint is the equivalent sweep for claims
(broken citations, stale claims, dangling refs) — pages have no sibling.

What you've tried

• wiki_render.backlinks() already computes the inbound-link map (used
  internally by render_moc), but nothing flags a page with zero entries.
• wiki_render.resolve_link() link resolution is only exercised at render
  time (silently drops anything unresolved) and at compile.py's
  draft-approval gate (_first_dangling_link rejects a new draft with a
  dangling link) — never as a standing check against the live, approved
  page set.
• compile.py's _citation_coverage() / MIN_CITATION_COVERAGE guardrail
  runs once, on a draft, before it's ever proposed — a page's body can
  drift after approval without re-triggering it.
• render-wiki already excludes archived pages from the front door (fix(wiki): render-wiki includes archived pages in index and MOC #695);
  nothing extends that policy to say a link into an archived page is
  dead.

Suggested shape

kb.wiki_lint — a page-level sibling to kb.lint, registered the same
way (MCP kb_wiki_lint, JSONL kb.wiki_lint, CLI vouch wiki-lint),
reusing wiki_render's link index/backlinks and compile's
citation-coverage walk rather than reimplementing either:

• orphan_page — zero inbound backlinks.
• dead_wikilink — a [[link]] that doesn't resolve against the live
  (non-archived) page set.
• stale_page — not updated in --stale-days (default 180, mirroring
  vouch lint --stale-days).
• uncited_section — citation coverage below --min-coverage (default
  0.5, mirroring compile.py's own MIN_CITATION_COVERAGE).

Suggested severities: orphan_page as info (a root/index page is
naturally unlinked, not inherently wrong), the other three as warning
(actionable, matching stale_claim's existing severity) — none as error,
since none represent a data-integrity violation the way broken_citation
or dangling_relation do.

Compatibility considerations

Purely additive, read-only, no VEP needed — no object model, on-disk
layout, or existing kb.* method signature changes. Like
wiki_render's index/MOC/backlinks, this is a derived view over already-
approved pages, so it doesn't touch proposals.py, lifecycle.py, or the
review gate at all.

Alternatives

Folding these checks into health.lint()/kb.lint directly instead of a
new method — rejected because lint()'s docstring scopes it explicitly to
claim/proposal health, and its stale_after_days parameter already means
something different (claim confirmation, not page edit recency); a shared
stale_days flag with two different semantics under one method would be
confusing. A dedicated method mirrors how kb.lint and kb.doctor are
already two separate entry points for two different sweep scopes.