Fix review findings and add static-analyzer agent

Review-fix batch (owner-confirmed) on the multi-agent harness:

- board_lock: detach holder stdio so a captured `hold` cannot hang on the
  daemon's inherited pipe; probe locks by holder-pid liveness instead of a
  momentary flock, which could spuriously fail a concurrent acquirer
  (storm-tested: 1 winner in 10, 0/15 acquire failures under probe storm)
- hil_test: locked board renders a visible board-locked fail row so the
  report matches the exit code; stale marker cleared on a real re-run
- pr-babysit: autoPush now opt-in (default dry run); resolve recipe
  paginates reviewThreads; post-push resolve gets issue-comment fallback
- validate: size stage honors non-default base via --base-branch; pvs
  stage delegated to the new agent
- new static-analyzer agent (sonnet): PVS-Studio SAST+MISRA for one
  board, structured findings gated on files changed vs base

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rn1AN5DsTdFhRwhugfgKZi

test/hil/board_lock.py

@@ -49,17 +49,22 @@ def read_info(board: str):
 
 
 def is_locked(board: str) -> bool:
-    """True if some live process currently holds the flock."""
-    path = lock_path(board)
-    if not os.path.exists(path):
+    """True if the recorded holder process is still alive.
+
+    Deliberately never touches the flock: even a momentary probe lock would
+    make a concurrent acquirer's LOCK_NB attempt fail spuriously. The flock
+    taken by acquirers themselves stays the only authority."""
+    info = read_info(board)
+    pid = info.get('pid') if isinstance(info, dict) else None
+    if not isinstance(pid, int) or pid <= 0:
         return False
-    with open(path) as f:
-        try:
-            fcntl.flock(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
-            fcntl.flock(f, fcntl.LOCK_UN)
-            return False
-        except OSError:
-            return True
+    try:
+        os.kill(pid, 0)
+    except ProcessLookupError:
+        return False
+    except PermissionError:
+        return True  # alive but owned by another user (e.g. the CI runner)
+    return True
 
 
 def cmd_hold(boards, reason):
@@ -91,6 +96,13 @@ def cmd_hold(boards, reason):
         os._exit(0)
     # holder (grandchild): acquire all flocks, signal the parent, sleep until killed
     os.close(r_fd)
+    # Detach stdio: a `hold` whose output is captured must see EOF when the
+    # front-end exits — the immortal holder must not keep that pipe open.
+    devnull = os.open(os.devnull, os.O_RDWR)
+    for std_fd in (0, 1, 2):
+        os.dup2(devnull, std_fd)
+    if devnull > 2:
+        os.close(devnull)
     try:
         handles = []
         for b in boards:

test/hil/hil_test.py

@@ -1704,7 +1704,9 @@ def test_board(board: Board) -> tuple[str, int, list[str], list]:
         _lock_fh = acquire_board_lock(name)
     except RuntimeError as e:
         log_line(f'{name:25} {STATUS_FAILED}: {e}')
-        return name, 1, [], []
+        # visible report row so the ❌ matches the exit code; failed-tests stays
+        # empty so a re-run repeats the whole board (no bogus -bt test filter)
+        return name, 1, [], [(name, {'board-locked': 'fail'})]
     try:
         # default to all tests
         test_list = []
@@ -1831,7 +1833,11 @@ def accumulate_report(mret: list, report_dir: Path, fresh: bool) -> str:
             pass  # corrupt/old sidecar: start fresh
 
     # merge this run: current cells override prior for boards/tests that ran
-    for _, _, _, rows in mret:
+    for name, _, _, rows in mret:
+        if rows and not any('board-locked' in cells for _, cells in rows):
+            # board ran for real this time: clear a stale lock-failure cell
+            # (its row is keyed by board name; test rows may be variant names)
+            acc.get(name, {}).pop('board-locked', None)
         for row_label, cells in rows:
             acc.setdefault(row_label, {}).update(cells)