feat(profiles): a faceted index policy and the additive STRUCTURED_V1 profile

The measured defect, as data: the 2026-08-26 bake-off had every arm retrieve
40/40, so quality could not separate them. The only axis that did was trap
exposure -- 18/20 for the OKF-index arm against 8/20 for a frontmatter
head-scan -- and both sides measured the reason independently: the flat index
carries title/date/status/supersedes 0 times while its own documents carry them
55/55/55/5. The metadata is in the bundle; the index throws it away.

FacetPolicy lets an index entry keep it. The grammar is thin on purpose (one
separator, then key: value joined by '; ') because index lines are read by
regex on both sides of this library, and a value carrying either delimiter is
REFUSED rather than escaped -- validation, not repair, as everywhere else here.

Additive by construction, not by caution. entry_pattern IS link_pattern when a
policy carries no facets, so DEFAULT and STRICT_V1 match the same lines and
emit the same bytes; the goldens are the proof. Facets arrive as STRUCTURED_V1,
a new profile, because DEFAULT states commons' ingest-spec index layer and
changing its bytes from here would be this repo editing a contract it does not
own.

17 new tests; suite 660 -> 677.

src/llm_ingestion_okf/materialize.py

@@ -271,7 +271,7 @@ def _update_index_lines(
     for line in lines:
         content = line.rstrip("\r\n")
         ending = line[len(content) :]
-        match = profile.index.link_pattern.match(content)
+        match = profile.index.entry_pattern.match(content)
         if match is not None:
             target = match.group("target")
             if target in removed_targets: