docs(okf): measure the tags/description gap against the pinned SPEC and corpus

Order 20260906T213322Z: measure and propose, no src, no bump. Measured against
SPEC _okf-canonical @ ad30107 and the corpus _okf-upstream @ 3fcbb9f (denominator
53, extracted at the pin because the work tree had moved on to 9a15b13).

Three claims in the tags/description entry are stale against the 1.3.0 parser.
The parser does have a sequence type -- _consume_block_list parses block lists of
scalars -- what it lacks is tolerance for the flush-left indentation 36/53 of the
corpus uses. Removing tags alone now lets 6/53 pass, not the 4/53 recorded, and
the entry's headline claim does not hold at all: description alone unblocks 0/53,
and with all three surface forms closed 44/53 still stop on generated as a
top-level block mapping. The entry oversells its own reach by a factor of seven.

The SPEC has no depth rule. no-nesting-past-depth-1 is entirely ours; the
conformance floor is only "a parseable YAML frontmatter block" (SS11.1).

Candidates were measured by normalizing the surface form onto a shape the parser
already accepts, then importing parse_frontmatter -- the predicate is never
re-implemented, only the input's spelling is rewritten. P1 (scalar flow sequence)
takes the corpus from 0/53 to 6/53 without spending depth-1; P2 and P3 buy 0/53
each and 6/53 stacked on P1. Recommendation is P1 alone, and the note says out
loud that this does not open the corpus.

The label "punkt 44" is not grep-able: it came from a count-after-insertion, and
the entry is today the 12th of 45 at docs/LIMITATIONS.md:126.

No src change, no version bump, no push. 868 passed, coverage 130/130 + 6/6 gaps,
redos sweep exit 0 -- all after git add.

.gitignore

@@ -24,3 +24,6 @@ coverage/
 *.local.md
 *.local.sh
 .DS_Store
+
+# --- scratchpad: measurement scripts are tracked, the extracted corpus copy is not ---
+/scratchpad/corpus/