fix(kanban): skip gone branches in merge-all instead of halting

merge-all halted with "merge: <branch> - not something we can merge" when a
candidate's branch ref no longer resolved (worktree+branch cleaned up
out-of-band while the run row lingered with branch set). That's not a
conflict — there's nothing for a resolution agent to do — yet it stopped
the whole batch.

- Verify each candidate resolves to a commit (resolveRef) before attempting;
  non-resolving branches are skipped (⤳) and the batch continues.
- Null the stale branch on the run row so it stops reappearing as a candidate.
- BatchMergeItem gains `skipped`; the modal shows skipped branches and counts
  them in the summary.
EOF && echo "" && git push 2>&1 | tail -4

apps/docs/src/components/kanban/MergeAllModal.tsx

@@ -56,6 +56,8 @@ export function MergeAllModal({ result, busy, onClose }: MergeAllModalProps) {
                 ` · ${result.items.filter((i) => i.conflict && i.ok).length} conflicts resolved by agent`}
               {result.items.some((i) => i.alreadyMerged) &&
                 ` · ${result.items.filter((i) => i.alreadyMerged).length} already in`}
+              {result.items.some((i) => i.skipped) &&
+                ` · ${result.items.filter((i) => i.skipped).length} skipped`}
               {result.haltedOn && ' · halted on conflict'}
             </p>
 
@@ -94,16 +96,31 @@ export function MergeAllModal({ result, busy, onClose }: MergeAllModalProps) {
             {result.items.length > 0 && (
               <div className="flex flex-col gap-2">
                 {result.items.map((item) => {
-                  const tone =
-                    item.alreadyMerged ? 'var(--muted)' : item.ok ? 'var(--green)' : 'var(--red)';
-                  const label = item.alreadyMerged
-                    ? 'already in target'
-                    : item.conflict && item.ok
-                      ? 'conflict resolved by agent'
+                  const tone = item.skipped
+                    ? 'var(--muted)'
+                    : item.alreadyMerged
+                      ? 'var(--muted)'
                       : item.ok
-                        ? 'merged'
-                        : 'conflict';
-                  const glyph = item.alreadyMerged ? '⇢' : item.conflict && item.ok ? '🤖' : item.ok ? '✓' : '⚠';
+                        ? 'var(--green)'
+                        : 'var(--red)';
+                  const label = item.skipped
+                    ? 'skipped (branch gone)'
+                    : item.alreadyMerged
+                      ? 'already in target'
+                      : item.conflict && item.ok
+                        ? 'conflict resolved by agent'
+                        : item.ok
+                          ? 'merged'
+                          : 'conflict';
+                  const glyph = item.skipped
+                    ? '⤳'
+                    : item.alreadyMerged
+                      ? '⇢'
+                      : item.conflict && item.ok
+                        ? '🤖'
+                        : item.ok
+                          ? '✓'
+                          : '⚠';
                   return (
                     <div
                       key={item.runId}

apps/docs/src/lib/orchestratorApi.ts

@@ -121,6 +121,9 @@ export interface BatchMergeItem extends MergeResult {
   conflict: boolean;
   /** When an agent resolved a conflict for this branch, its run id; else null. */
   resolutionRunId: string | null;
+  /** True if the branch no longer resolves (cleaned up but the row lingered) —
+   * skipped, batch continues. */
+  skipped: boolean;
 }
 
 /** Result of merging several branches sequentially into the main branch. */