feat(p22): a refusal names the DOCUMENTS when the ancestor has no subdirectories

P21/C2 made a refusal for an absent path name the ancestor's SUBDIRECTORIES, and it bought what it
was built for: read_dir against a level the base does not hold went from 16 of 104 to 8 of 128. It
did nothing for documents -- read_file against a document the base does not hold went 2 of 38 to
7 of 52 -- and the reason is structural: the nearest listable ancestor of a guessed DOCUMENT path
often holds documents and no subdirectories, and then the neighbour clause was omitted, deliberately,
because an empty list is a sentence with nothing in it.

Measured over round 5's six read_file misses, THREE land on such an ancestor: krav/N100 with 445
documents, and R761/1 with exactly ONE -- which two separate guesses in one run were both reaching
for. The other three have subdirectories and were already answered.

okf.nearest_documents is the sibling of nearest_subdirectories, never a widening of it: never both
clauses, and the subdirectory branch stays FIRST, which is what keeps every C2 refusal byte-identical.
Built from context_files and through the same in_dimension predicate the listing uses, so a refusal
can never advertise the type: verdict layer by path, and every name it hands back resolves -- measured
by feeding each one back into read_file, not by asserting the list is non-empty.

A MUTATION FOUND THE RANKING UNWITNESSED, and that is recorded rather than dropped: replacing
_shared_prefix with a plain reverse sort left the whole suite green. The bound, the source and the
resolve property were all gated; the ORDER was not. For R761/1 that costs nothing, but a level of a
delivered corpus can hold 445, and then which five it names is the whole value of the clause. The new
arm builds a level where the closest name is also the LONGEST, so a length rule puts it last and an
alphabetical one puts another first -- only the prefix rule puts it first.

Load-bearing MEASURED (tests/test_document_neighbours_loadbearing.py, 10 arms), seven mutations all
red against the WHOLE suite + green control 1891/5 (from 1881/5, superset, 0 removed) and golden
demo-transcript.stdout BYTE-UNCHANGED (shasum -a 1 of the CONTENT =
ea8c534773acdbe41ae68f2c55724d69aaf8be4f): C1 detach the document branch in read_file (5 red) -
C2 detach it in read_dir (1) - C3 build from files (1) - C4 ignore the dimension (1) - C5 no bound
(1) - C6 both clauses at once (1) - C7 a second ranking rule (1, after the test was fixed; green
before, which is the finding).

Honesty limits, stated: the foreign-dimension arm was VACUOUSLY green before this change (nothing
was named, so nothing could leak) and is gated only now -- C4 is what makes it real; no LIVE model
has read the new clause (DEL D is the measurement); and the clause is help text, not a gate -- it
cannot make a guessed path right, only cheaper to correct.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -796,7 +796,11 @@ when the seam is detached, so the loop cannot silently degrade into theater.
   none of the thirteen named a right one. The refusal is a turn the model can correct, and it
   carries both numbers. A path the base does not hold is likewise refused by name, and the refusal
   now lists up to five subdirectories of the nearest directory that does hold documents — every one
-  of them a path `read_dir` will answer for.
+  of them a path `read_dir` will answer for. When that directory has no subdirectories at all, the
+  refusal names up to five of the DOCUMENTS it holds instead, on the same rule and with the same
+  property: each name resolves. (Measured over one stress round, three of six guessed document
+  paths landed on such a directory and got no suggestion at all — including two separate guesses,
+  in one run, at the name of the single document that level holds.)
 
   Every tool call recorded in `{run_id}-exploration.json` and `{run_id}-debate.json` says HOW the
   level was asked for — `filter`, `offset` and `limit` beside the tool name, the base and the path