fix(sync): add missing coverage scenarios and remove dead _iso_now from sync_models

- Remove unused _iso_now() from sync_models.py (dead code: called nowhere in
  the module; sync_service.py has its own _iso_now())
- Remove now-unused `from datetime import UTC, datetime` import
- Add 5 new BDD scenarios covering previously uncovered code paths:
  - VectorClock.happens_before() TypeError guard (sync_models.py:134-135)
  - VectorClock.is_concurrent() TypeError guard (sync_models.py:159-160)
  - process_offline_queue() PULL direction branch (sync_service.py:468-475)
  - resolve_conflict() last_writer_wins when server entity is newer (sync_service.py:549 else)
  - SyncService.push() with CLIENT_WINS resolution (_resolve_conflict lines 663-665)
- Add corresponding step implementations for the new scenarios

ISSUES CLOSED: #1125

features/entity_sync.feature

@@ -416,3 +416,37 @@ Feature: Entity sync via _cleveragents/sync/*
     And a local actor snapshot for offline queuing
     When I enqueue an offline pull from namespace "team"
     Then the offline queue should have 1 entry
+
+  Scenario: Vector clock happens_before rejects non-VectorClock
+    Given an empty vector clock
+    When I try to call happens_before with a non-VectorClock value
+    Then a sync TypeError should be raised
+
+  Scenario: Vector clock is_concurrent rejects non-VectorClock
+    Given an empty vector clock
+    When I try to call is_concurrent with a non-VectorClock value
+    Then a sync TypeError should be raised
+
+  Scenario: Process offline queue processes pull operation
+    Given a sync service with node_id "test-client"
+    And server entities in namespace "team" with 1 actors
+    And a local actor snapshot for offline queuing
+    When I enqueue an offline pull from namespace "team"
+    And I process the offline queue
+    Then the processed entries should include the offline actor
+    And the offline queue should be empty
+
+  Scenario: Resolve conflict with last_writer_wins picks server when newer
+    Given a sync service with node_id "test-client"
+    And an unresolved conflict where server is newer
+    When I resolve the conflict with last_writer_wins strategy
+    Then the conflict should be marked as resolved
+    And the conflict winner should be "server"
+
+  Scenario: Push with client_wins resolution accepts local entity
+    Given a sync service with node_id "test-client"
+    And a local actor "conflict-actor" in namespace "team" with clock {"client": 2, "server": 1}
+    And a server actor "conflict-actor" in namespace "team" with clock {"client": 1, "server": 2}
+    When I push the local actor to namespace "team" with client-wins resolution
+    Then the push response should have 1 accepted
+    And the push conflict winner should be "local"

features/steps/entity_sync_steps.py

@@ -119,6 +119,24 @@ def step_merge_non_clock(context: Any) -> None:
         context.caught_exception = exc
 
 
+@when("I try to call happens_before with a non-VectorClock value")
+def step_happens_before_bad_type(context: Any) -> None:
+    context.caught_exception = None
+    try:
+        context.clock1.happens_before("not a clock")  # type: ignore[arg-type]
+    except TypeError as exc:
+        context.caught_exception = exc
+
+
+@when("I try to call is_concurrent with a non-VectorClock value")
+def step_is_concurrent_bad_type(context: Any) -> None:
+    context.caught_exception = None
+    try:
+        context.clock1.is_concurrent("not a clock")  # type: ignore[arg-type]
+    except TypeError as exc:
+        context.caught_exception = exc
+
+
 # ------------------------------------------------------------------
 # Model validation steps
 # ------------------------------------------------------------------
@@ -445,6 +463,28 @@ def step_setup_unresolved_conflict(context: Any) -> None:
     context.conflict_id = svc.conflicts[0].conflict_id
 
 
+@given("an unresolved conflict where server is newer")
+def step_setup_conflict_server_newer(context: Any) -> None:
+    svc: SyncService = context.sync_service
+    local_entity = _make_actor_snapshot(
+        entity_id="ts-conflict-srv",
+        namespace="team",
+        clock_entries={"client": 2, "server": 1},
+        updated_at="2025-01-01T00:00:00+00:00",
+    )
+    server_entity = _make_actor_snapshot(
+        entity_id="ts-conflict-srv",
+        namespace="team",
+        clock_entries={"client": 1, "server": 2},
+        updated_at="2025-07-01T00:00:00+00:00",
+    )
+    svc.register_local_entity(local_entity)
+    svc.register_server_entity(server_entity)
+    pull_req = SyncPullRequest(namespace="team")
+    svc.pull(pull_req)
+    context.conflict_id = svc.conflicts[0].conflict_id
+
+
 @given("an unresolved conflict where local is newer")
 def step_setup_conflict_local_newer(context: Any) -> None:
     svc: SyncService = context.sync_service
@@ -581,6 +621,16 @@ def step_push_server_wins(context: Any, namespace: str) -> None:
     context.push_response = context.sync_service.push(request)
 
 
+@when('I push the local actor to namespace "{namespace}" with client-wins resolution')
+def step_push_client_wins(context: Any, namespace: str) -> None:
+    request = SyncPushRequest(
+        namespace=namespace,
+        entities=[context.local_entity],
+        resolution=ConflictResolution.CLIENT_WINS,
+    )
+    context.push_response = context.sync_service.push(request)
+
+
 @when('I push the local actor to namespace "{namespace}" with manual resolution')
 def step_push_manual(context: Any, namespace: str) -> None:
     request = SyncPushRequest(

src/cleveragents/a2a/sync_models.py

@@ -9,7 +9,6 @@ The ``local/`` namespace is **never** synced — it exists only on the client.
 
 from __future__ import annotations
 
-from datetime import UTC, datetime
 from enum import StrEnum
 from typing import Any
 
@@ -379,11 +378,6 @@ class SyncQueueEntry(BaseModel):
         return value
 
 
-def _iso_now() -> str:
-    """Return the current UTC time as an ISO-8601 string."""
-    return datetime.now(tz=UTC).isoformat()
-
-
 __all__ = [
     "ConflictResolution",
     "SyncConflict",