fix(reaper): tighten research-session pattern to literal YYYY-MM-DD shape

Apply Ganymede review of 50b888a:

MUST-FIX — pattern %/research-2% was broader than the comment claimed.
Matched anything/research-2[anything] including agent-named branches like
theseus/research-2nd-attempt-on-X or vida/research-2024-revisited. The
documented invariant said "date suffix only" but the SQL didn't enforce
it. Defense-in-depth was the framing; pattern needed to match the
framing.

Fix uses SQLite `_` single-char wildcards: research-20__-__-__ requires
exactly research-20[2-char][-][2-char][-][2-char], i.e. literal
YYYY-MM-DD shape. Threads the needle:
  - theseus/research-2026-04-30  ✓ (catches all 15 currently stuck)
  - rio/research-2099-12-31      ✓ (good through 2099)
  - theseus/research-2nd-attempt ✗ (correctly excluded)
  - vida/research-2024-revisited ✗ (correctly excluded — no -MM-DD shape)
  - rio/research-batch-agents-... ✗ (no date prefix at all)

NIT — comment said "Three classes qualify" then listed four. Off-by-one
fixed; comment now correctly says "Four classes."

Pre-deploy verified: tighter pattern catches all 15 currently-stuck
research PRs (clay/leo/astra/theseus/vida/rio research-2026-{04-28
through 05-02}). Zero false-positive risk on current branch namespace.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/substantive_fixer.py

@@ -647,10 +647,28 @@ async def verdict_deadlock_reaper_cycle(conn) -> int:
             return 0
 
     # Two stuck-verdict shapes: leo:rc+domain:approve, leo:skipped+domain:rc.
-    # Branch allowlist scopes the reaper to disposable pipeline-managed branches.
-    # extract/, reweave/, fix/ are content the pipeline created and can recreate;
-    # agent branches (theseus/, vida/, epimetheus/, etc.) are WIP feature work
-    # and must not be reaped — owners review their own PRs on their own cadence.
+    #
+    # Branch allowlist invariant: the reaper closes ONLY disposable, pipeline-
+    # generated branches — content the pipeline (or a daily cron) created and
+    # can recreate. Four classes qualify:
+    #
+    #   extract/* — per-source extraction PRs, regenerated next ingest cycle
+    #   reweave/* — nightly graph-edge maintenance, regenerated next reweave
+    #   fix/*     — pipeline-internal fix branches
+    #   */research-YYYY-MM-DD — daily {agent}/research-{date} cron sessions.
+    #                   Matched via SQLite `_` single-char wildcards as
+    #                   `research-20__-__-__` to literally enforce the date-
+    #                   suffix shape. Excludes hand-named research branches
+    #                   (rio/research-batch-agents-memory-harnesses,
+    #                   theseus/research-2nd-attempt-on-X, etc.) which are
+    #                   feature work owned by the agent. Pattern good through
+    #                   2099; revisit then.
+    #
+    # WIP agent feature branches (theseus/feature-foo, epimetheus/some-fix,
+    # rio/research-thesis-name) are NEVER reaped — owners review their own PRs
+    # on their own cadence. The date-shaped pattern threads the needle: picks
+    # up daily synthesis output the agent regenerates tomorrow while leaving
+    # manually-named research work alone.
     rows = conn.execute(
         """SELECT number, branch, eval_issues, leo_verdict, domain_verdict,
                   last_attempt, fix_attempts
@@ -659,7 +677,10 @@ async def verdict_deadlock_reaper_cycle(conn) -> int:
            AND tier0_pass = 1
            AND last_attempt IS NOT NULL
            AND last_attempt < datetime('now', ? || ' hours')
-           AND (branch LIKE 'extract/%' OR branch LIKE 'reweave/%' OR branch LIKE 'fix/%')
+           AND (branch LIKE 'extract/%'
+                OR branch LIKE 'reweave/%'
+                OR branch LIKE 'fix/%'
+                OR branch LIKE '%/research-20__-__-__')
            AND (
                (leo_verdict = 'request_changes' AND domain_verdict = 'approve')
                OR (leo_verdict = 'skipped' AND domain_verdict = 'request_changes')