snapshot: WIP 5j replay reliability (B1 watchdog + dialog handlers + grounding drift)

Snapshot avant correction du blocage relance Léa (3 incidents 24h: SSH refusé,
polls morts ×2). Point de rollback stable.

Contenu:
- agent_v1/core/executor.py: 5 patchs dialog handling (saveas drift, close_tab
  hotkey fallback, confirm_save Unicode apostrophe, foreground dialog
  recontextualization, runtime_dialog in-loop) + helpers normalize_window_hint,
  requires_post_verify_window_transition
- agent_v1/core/grounding.py: garde drift template fix (fallback_x/y plumbed)
- server_v1/replay_watchdog.py (NEW): orphan watchdog B1, scan 10s timeout 30s
- server_v1/api_stream.py: dispatched_action plumbing, watchdog lifespan,
  metrics endpoint
- server_v1/replay_engine.py: _schedule_retry préserve original_action +
  dispatched_action
- stream_processor.py: gardes _infer_tab_switch_target (no false switch_tab
  on save_as dialog open) + _attach_expected_window_before
- tests/integration: test_replay_watchdog.py (8 cas), test_stream_processor.py
- tests/unit: test_executor_verify_window_guard.py (start_button, close_tab,
  runtime_dialog, post_verify, transition fallbacks)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/test_grounding_engine.py

@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock
+
+ROOT = Path(__file__).parent.parent.parent
+sys.path.insert(0, str(ROOT))
+
+from agent_v0.agent_v1.core.grounding import GroundingEngine  # noqa: E402
+
+
+def test_template_strategy_passes_fallback_coords_to_anchor_drift_guard():
+    executor = MagicMock()
+    executor._template_match_anchor = MagicMock(
+        return_value={
+            "resolved": True,
+            "x_pct": 0.7,
+            "y_pct": 0.35,
+            "score": 0.95,
+        }
+    )
+
+    engine = GroundingEngine(executor)
+    target_spec = {"anchor_image_base64": "abc123"}
+
+    result = engine._try_strategy(
+        "template",
+        server_url="",
+        screenshot_b64="shot",
+        target_spec=target_spec,
+        fallback_x=0.708594,
+        fallback_y=0.35,
+        screen_width=2560,
+        screen_height=1600,
+    )
+
+    assert result.found is True
+    executor._template_match_anchor.assert_called_once_with(
+        "shot",
+        "abc123",
+        2560,
+        1600,
+        fallback_x_pct=0.708594,
+        fallback_y_pct=0.35,
+    )