fix(governor): apply reviewer fixes for dead code, import scope, and DB persistence

(cherry picked from commit 37c0a1ae41)

backend/app/schemas/auto_heartbeat_governor.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import re
 from enum import Enum
 from typing import Annotated
 
@@ -32,8 +33,6 @@ def _validate_duration(value: str) -> str:
         raise ValueError('duration cannot be "disabled"')
     # Simple format: integer + unit.
     # Keep permissive for future; server-side logic still treats these as opaque.
-    import re
-
     if not re.match(r"^\d+\s*[smhd]$", value, flags=re.IGNORECASE):
         raise ValueError("duration must match ^\\d+[smhd]$")
     return value.replace(" ", "")

backend/app/services/auto_heartbeat_governor.py

@@ -95,9 +95,7 @@ def compute_desired_heartbeat(
 
     if is_lead:
         # Leads never go fully off; cap at lead_cap_every.
-        if next_step <= 0:
-            next_every = active_every
-        elif next_step <= len(ladder):
+        if next_step <= len(ladder):
             next_every = ladder[next_step - 1]
         else:
             next_every = lead_cap_every
@@ -308,19 +306,22 @@ async def run_governor_once() -> None:
                             (agent_id, workspace_path, heartbeat_payload),
                         )
 
-                if needs_db:
+                # Keep heartbeat_config in sync for non-off entries.
+                needs_heartbeat_config_update = (
+                    desired.every is not None and agent.heartbeat_config != heartbeat_payload
+                )
+
+                if needs_db or needs_heartbeat_config_update:
                     agent.auto_heartbeat_step = desired.step
                     agent.auto_heartbeat_off = desired.off
-                    if active:
+                    if active and needs_db:
                         agent.auto_heartbeat_last_active_at = now
+                    if needs_heartbeat_config_update:
+                        agent.heartbeat_config = heartbeat_payload
                     agent.updated_at = now
                     session.add(agent)
                     changed += 1
 
-                # Keep heartbeat_config in sync for non-off entries.
-                if desired.every is not None:
-                    agent.heartbeat_config = heartbeat_payload
-
             if changed:
                 await session.commit()