fix(state): doctor's holder count enumerates macOS holders via libproc (#109641)

`count_db_holders` returned None on every non-Linux host, so `hermes doctor`
on macOS (every reporter in the deleted-WAL cluster) printed no
"N process(es) holding the DB open" row. The libproc enumeration that #110544
landed for the sidecar scan already yields `(pid, fd, path, (st_dev, st_ino))`;
count distinct PIDs whose fd identity matches state.db's inode. Identity, not
pathname: libproc reports the path as the opener spelled it (case, symlinked
prefix), which is what the sidecar leg had to case-fold around.

Carries the surviving delta from #110023 (@kshitijk4poor), whose libproc leg
otherwise landed via #110544.

hermes_state_dbfile.py

@@ -765,13 +765,19 @@ def collect_state_db_stats(db_path: Path) -> Dict[str, Any]:
 
 
 def count_db_holders(db_path: Path) -> Optional[int]:
-    """Best-effort count of distinct PIDs holding ``db_path`` open (``/proc/*/fd`` scan); ``None``
+    """Best-effort count of distinct PIDs holding ``db_path`` open (``/proc/*/fd`` on Linux, libproc
-    on any error or non-Linux host, never raises.  Unreadable fd dirs (other users' processes
+    on macOS); ``None`` on any error or other host, never raises.  Uninspectable processes (other
-    without root) are skipped, so this is a lower bound."""
+    users' without root) are skipped, so this is a lower bound."""
     try:
+        target = os.path.realpath(str(db_path))
+        if sys.platform == "darwin":
+            # Identity, not pathname: libproc reports the vnode's last name as the opener spelled it
+            # (case, symlinked prefix), which is exactly what the sidecar leg had to case-fold around.
+            st = os.stat(target)
+            identity = (st.st_dev, st.st_ino)
+            return len({pid for pid, _fd, _path, ident in _iter_darwin_fd_targets() if ident == identity})
         if not sys.platform.startswith("linux"):
             return None
-        target = os.path.realpath(str(db_path))
         return len({pid for pid, link, _fd_path in _iter_proc_fd_targets() if link == target})
     except Exception:
         return None

tests/hermes_state/test_state_db_stats.py

@@ -4,8 +4,8 @@ Covers:
 - ``hermes_state_dbfile.collect_state_db_stats``: read-only, best-effort stats
   (page_count, freelist, WAL size, journal mode, row counts, FTS presence,
   pending v23 FTS-rebuild bookkeeping).
-- ``hermes_state_dbfile.count_db_holders``: /proc-based best-effort probe for how
+- ``hermes_state_dbfile.count_db_holders``: best-effort probe for how many processes
-  many processes hold the DB file open (Linux only; None elsewhere/on error).
+  hold the DB file open (/proc on Linux, libproc on macOS; None elsewhere/on error).
 - ``hermes_cli.doctor_state._render_state_db_stats``: formatting/threshold helper
   the doctor state.db section prints from.
 """
@@ -14,7 +14,6 @@ import hermes_state_dbfile
 import json
 import os
 import sqlite3
-import sys
 from pathlib import Path
 
 import pytest
@@ -138,19 +137,28 @@ def test_collect_stats_rebuild_pending_flag(populated_db):
 # ── count_db_holders ────────────────────────────────────────────────────
 
 
-def test_count_db_holders_sees_open_connection(populated_db):
+def _assert_sees_own_open_connection(db_path):
-    conn = sqlite3.connect(str(populated_db))
+    conn = sqlite3.connect(str(db_path))
     try:
-        holders = count_db_holders(populated_db)
+        holders = count_db_holders(db_path)
-        if sys.platform.startswith("linux"):
+        assert isinstance(holders, int)
-            assert isinstance(holders, int)
+        assert holders >= 1
-            assert holders >= 1
-        else:
-            assert holders is None
     finally:
         conn.close()
 
 
+@pytest.mark.linux_only
+def test_count_db_holders_sees_open_connection_linux(populated_db):
+    _assert_sees_own_open_connection(populated_db)
+
+
+@pytest.mark.macos_only
+def test_count_db_holders_sees_open_connection_macos(populated_db):
+    # #109641: the doctor's holder count was Linux-only, so `hermes doctor` on the platform with
+    # every reporter in the deleted-WAL cluster printed no holder row at all.
+    _assert_sees_own_open_connection(populated_db)
+
+
 def test_count_db_holders_missing_path_no_raise(tmp_path):
     holders = count_db_holders(tmp_path / "absent.db")
     assert holders is None or isinstance(holders, int)