fix(gateway): quiet corrupt kanban dispatcher boards

Salvages substantive part of #26490 by @aqilaziz. Detects corrupt board
DBs ("file is not a database" / "database disk image is malformed")
and disables them by fingerprint until they're repaired, instead of
flooding the gateway log with repeated logger.exception tracebacks every
tick.

Cherry-picked the substantive commit (ea5b4ec2a); the tip commit was
an unrelated _is_dir OSError fix for service-path lookup. Dropped a
small test reformat that was bundled in the same commit.

tests/hermes_cli/test_kanban_core_functionality.py

@@ -3594,6 +3594,82 @@ def test_gateway_dispatcher_watcher_env_truthy_uses_config(monkeypatch):
     )
 
 
+def test_gateway_dispatcher_disables_corrupt_board_without_traceback(
+    monkeypatch, tmp_path, caplog
+):
+    """Corrupt board DBs log one actionable error and stop retrying per tick."""
+    import asyncio
+    import logging
+    import sqlite3
+
+    from gateway.run import GatewayRunner
+    import hermes_cli.config as _cfg_mod
+    import hermes_cli.kanban_db as _kb
+
+    runner = object.__new__(GatewayRunner)
+    runner._running = True
+    corrupt_db = tmp_path / "kanban.db"
+    corrupt_db.write_text("not sqlite", encoding="utf-8")
+
+    monkeypatch.setattr(
+        _cfg_mod,
+        "load_config",
+        lambda: {
+            "kanban": {
+                "dispatch_in_gateway": True,
+                "dispatch_interval_seconds": 1,
+            }
+        },
+    )
+    monkeypatch.setattr(
+        _kb,
+        "list_boards",
+        lambda include_archived=False: [{"slug": _kb.DEFAULT_BOARD}],
+    )
+    monkeypatch.setattr(
+        _kb,
+        "read_board_metadata",
+        lambda slug: {"slug": slug},
+    )
+    monkeypatch.setattr(_kb, "kanban_db_path", lambda board=None: corrupt_db)
+
+    calls = {"connect": 0, "to_thread": 0}
+
+    def _connect(*args, **kwargs):
+        calls["connect"] += 1
+        raise sqlite3.DatabaseError("file is not a database")
+
+    async def _to_thread(fn, *args, **kwargs):
+        calls["to_thread"] += 1
+        result = fn(*args, **kwargs)
+        if calls["to_thread"] >= 4:
+            runner._running = False
+        return result
+
+    async def _sleep(_delay):
+        return None
+
+    monkeypatch.setattr(_kb, "connect", _connect)
+    monkeypatch.setattr("gateway.run.asyncio.to_thread", _to_thread)
+    monkeypatch.setattr("gateway.run.asyncio.sleep", _sleep)
+
+    with caplog.at_level(logging.ERROR, logger="gateway.run"):
+        asyncio.run(
+            asyncio.wait_for(
+                runner._kanban_dispatcher_watcher(),
+                timeout=3.0,
+            )
+        )
+
+    messages = [record.getMessage() for record in caplog.records]
+    assert sum("not a valid SQLite database" in msg for msg in messages) == 1
+    assert not any("tick failed on board" in msg for msg in messages)
+    assert not any(record.exc_info for record in caplog.records)
+    # First tick connect + two ready-queue probes. The second dispatch tick
+    # skips connect because the corrupt board fingerprint is disabled.
+    assert calls["connect"] == 3
+
+
 # ---------------------------------------------------------------------------
 # Hallucination gate (created_cards verify + prose scan)
 # ---------------------------------------------------------------------------