feat(scripts): OKF conformance linter, trash-aware vault seams

Add scripts/check-okf.py: enforces the OKF v0.1 hard rules the repo had
been carrying by convention — parseable frontmatter with type/title/
description/timestamp, description shape (length, not-equals-title, no
restated quantity), the reserved-name and index.md rules, log.md's date
heading shape (bare ISO date, one entry per date, newest first), the
500-line hint, and the doubled-page signature (a second `type:` key in
the body). Citations are reported as a soft tally, not a failure. The
500-line ceiling is escapable two ways, both explainable: `okf-exempt:
length` in a page's own frontmatter, and pages derived as one-per-
endpoint — live endpoints from scripts/, retired-endpoint era pages from
their tag (AGENTS.md lets a campaign ledger live on the page that
measured it).

scripts/gen-vault-index.py: sibling-presence was tested as a bare stem
substring, so a page whose name is a prefix of another page's name
(`frank-medium` inside `frank-medium-rocmfpx`) silently never got an
index row. Test the wikilink form instead.

scripts/check-vault-links.py: `.AGENTTRASH` is deleted-but-held state,
not vault content. It is now excluded from both the scan set and the
target index, so a live link into the trash reads as unresolved instead
of resolved.

tests/docs_completeness.bats: the same exclusion in both page walks —
trashed pages need no index row, and a trashed page must not satisfy the
docs requirement for a live compose service. Adds the OKF conformance
and index-freshness tests.

scripts/port-census.py: the port-before-cut orphan census used to prove
a merge lost no fact, kept so the next collapse can re-run it.

scripts/check-vault-links.py

@@ -31,7 +31,12 @@ def strip_md(path: str) -> str:
 
 
 def build_index(vault: pathlib.Path):
-    pages = sorted(vault.rglob("*.md"))
+    # `.AGENTTRASH` is deleted-but-held state, not vault content: it must not be
+    # scanned (its relative links resolve against the trash dir, not the vault)
+    # and must not answer as a link target — a live page pointing into the trash
+    # is an unresolved link, not a resolved one.
+    pages = sorted(p for p in vault.rglob("*.md")
+                   if ".AGENTTRASH" not in str(p))
     stems: dict[str, list[pathlib.Path]] = {}
     for page in pages:
         stems.setdefault(page.stem.casefold(), []).append(page)