fix: fix: triage agent must clean up throwaway debug branch on exit/crash (#341)

Add an EXIT trap in entrypoint-reproduce.sh that:
- Switches back to the primary branch
- Deletes the triage-debug-${ISSUE_NUMBER} branch

This ensures the throwaway branch used for debug instrumentation
(console.log, verbose logging) is cleaned up if the agent crashes
or times out, preventing repository pollution.

The trap is combined with existing cleanup (heartbeat kill, stack
lock release) into a single EXIT handler.

docker/reproduce/entrypoint-reproduce.sh

@@ -140,7 +140,6 @@ log "Issue: ${ISSUE_TITLE}"
 # ---------------------------------------------------------------------------
 log "Acquiring stack lock for project ${PROJECT_NAME}..."
 stack_lock_acquire "$LOCK_HOLDER" "$PROJECT_NAME" 900
-trap 'stack_lock_release "$PROJECT_NAME" "$LOCK_HOLDER"; log "Stack lock released (trap)"' EXIT
 log "Stack lock acquired."
 
 # ---------------------------------------------------------------------------
@@ -154,7 +153,18 @@ heartbeat_loop() {
 }
 heartbeat_loop &
 HEARTBEAT_PID=$!
-trap 'kill "$HEARTBEAT_PID" 2>/dev/null; stack_lock_release "$PROJECT_NAME" "$LOCK_HOLDER"; log "Stack lock released (trap)"' EXIT
+
+# ---------------------------------------------------------------------------
+# Debug branch cleanup trap (for triage-agent throwaway branches)
+# ---------------------------------------------------------------------------
+DEBUG_BRANCH="triage-debug-${ISSUE_NUMBER}"
+
+# Combined EXIT trap: heartbeat kill + stack lock release + debug branch cleanup
+trap 'kill "$HEARTBEAT_PID" 2>/dev/null || true
+  stack_lock_release "$PROJECT_NAME" "$LOCK_HOLDER" || true
+  git -C "$PROJECT_REPO_ROOT" checkout "$PRIMARY_BRANCH" 2>/dev/null || true
+  git -C "$PROJECT_REPO_ROOT" branch -D "$DEBUG_BRANCH" 2>/dev/null || true
+  log "Cleanup completed (trap)"' EXIT
 
 # ---------------------------------------------------------------------------
 # Boot the project stack if formula declares stack_script