fix: replace broken _rebase_and_push call with cherry-pick in conflict retry

_retry_conflict_prs called _rebase_and_push which was never defined,
causing NameError on every conflict retry. Now uses _cherry_pick_onto_main
consistent with the primary merge path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/merge.py

@@ -178,9 +178,8 @@ async def _claim_next_pr(conn, domain: str) -> dict | None:
     """
     # Build prefix filter for pipeline-owned branches only
     # Agent branches stay approved but are NOT auto-merged (Leo: PRs #2141, #157, #2142, #2180)
-    prefix_clauses = " OR ".join(
-        f"p.branch LIKE '{pfx}%'" for pfx in PIPELINE_OWNED_PREFIXES
-    )
+    prefix_clauses = " OR ".join("p.branch LIKE ?" for _ in PIPELINE_OWNED_PREFIXES)
+    prefix_params = [f"{pfx}%" for pfx in PIPELINE_OWNED_PREFIXES]
     row = conn.execute(
         f"""UPDATE prs SET status = 'merging', last_attempt = datetime('now')
         WHERE number = (
@@ -210,7 +209,7 @@ async def _claim_next_pr(conn, domain: str) -> dict | None:
             LIMIT 1
         )
         RETURNING number, source_path, branch, domain""",
-        (domain,),
+        (domain, *prefix_params),
     ).fetchone()
     return dict(row) if row else None
 
@@ -329,8 +328,10 @@ async def _cherry_pick_onto_main(branch: str) -> tuple[bool, str]:
 
                 if conflict_files and all(f.startswith("entities/") for f in conflict_files):
                     # Entity conflicts: take main's version (entities are recoverable)
+                    # In cherry-pick: --ours = branch we're ON (clean branch from origin/main)
+                    #                 --theirs = commit being cherry-picked (extraction branch)
                     for cf in conflict_files:
-                        await _git("checkout", "--theirs", cf, cwd=worktree_path)
+                        await _git("checkout", "--ours", cf, cwd=worktree_path)
                         await _git("add", cf, cwd=worktree_path)
                     dropped_entities.update(conflict_files)
                     rc_cont, cont_out = await _git(
@@ -366,7 +367,9 @@ async def _cherry_pick_onto_main(branch: str) -> tuple[bool, str]:
         # Force-push clean branch as the original branch name
         # Capture expected SHA for force-with-lease
         rc, expected_sha = await _git("rev-parse", f"origin/{branch}")
-        expected_sha = expected_sha.strip().split("\n")[0] if rc == 0 else ""
+        if rc != 0:
+            return False, f"rev-parse origin/{branch} failed: {expected_sha}"
+        expected_sha = expected_sha.strip().split("\n")[0]
 
         rc, out = await _git(
             "push",
@@ -972,8 +975,8 @@ async def _merge_domain_queue(conn, domain: str) -> tuple[int, int]:
                 failed += 1
                 continue
 
-            # Local ff-merge: push rebased branch as main (Rhea's approach, Leo+Rhea: local primary)
-            # The branch was just rebased onto origin/main by _rebase_and_push,
+            # Local ff-merge: push cherry-picked branch as main (Rhea's approach, Leo+Rhea: local primary)
+            # The branch was just cherry-picked onto origin/main,
             # so origin/{branch} is a descendant of origin/main. Push it as main.
             await _git("fetch", "origin", branch, timeout=15)
             rc, main_sha = await _git("rev-parse", "origin/main")
@@ -1256,13 +1259,13 @@ async def _handle_permanent_conflicts(conn) -> int:
 
 
 async def _retry_conflict_prs(conn) -> tuple[int, int]:
-    """Retry rebase on conflict PRs that were previously approved.
+    """Retry conflict PRs via cherry-pick onto fresh main.
 
     Design: Ganymede (extend merge stage), Rhea (safety guards), Leo (re-eval required).
     - Pick up PRs with status='conflict' and both approvals
-    - Attempt fresh rebase onto origin/main
-    - If rebase succeeds: force-push, reset to 'open' with verdicts cleared for re-eval
-    - If rebase fails: increment attempt counter, leave as 'conflict'
+    - Cherry-pick extraction commits onto fresh branch from origin/main
+    - If cherry-pick succeeds: force-push, reset to 'open' with verdicts cleared for re-eval
+    - If cherry-pick fails: increment attempt counter, leave as 'conflict'
     - After MAX_CONFLICT_REBASE_ATTEMPTS failures: mark 'conflict_permanent'
     - Skip branches with new commits since conflict was set (Rhea: someone is working on it)
     """
@@ -1293,8 +1296,8 @@ async def _retry_conflict_prs(conn) -> tuple[int, int]:
         await _git("fetch", "origin", branch, timeout=30)
         await _git("fetch", "origin", "main", timeout=30)
 
-        # Attempt rebase
-        ok, msg = await _rebase_and_push(branch)
+        # Attempt cherry-pick onto fresh main (replaces rebase — Leo+Cory directive)
+        ok, msg = await _cherry_pick_onto_main(branch)
 
         if ok:
             # Rebase succeeded — reset for re-eval (Ganymede: approvals are stale after rebase)