refactor(apply_patch): remove deprecated patch mode, keep edits-only

Drop the legacy unified-diff patch parameter and all related parsing/
generation logic (_parse_patch, _generate_patch, _apply_hunks, etc.).
The tool now accepts only the structured `edits` array, eliminating the
intermediate diff-string round-trip.

Also update file_edit_events tracking and tests to work exclusively
with edits.

Benchmark (zhipu glm-5.1, edits mode): 15/15 cases passed.

tests/utils/test_file_edit_events.py

@@ -89,23 +89,18 @@ def test_apply_patch_prepares_trackers_for_each_touched_file(tmp_path: Path) ->
     delete_me = tmp_path / "src" / "delete_me.py"
     delete_me.write_text("gone\n", encoding="utf-8")
 
-    patch = """*** Begin Patch
-*** Add File: src/new.py
-+fresh
-*** Update File: src/existing.py
-@@
--old
-+new
- keep
-*** Delete File: src/delete_me.py
-*** End Patch"""
+    edits = [
+        {"path": "src/new.py", "action": "add", "new_text": "fresh"},
+        {"path": "src/existing.py", "action": "replace", "old_text": "old", "new_text": "new"},
+        {"path": "src/delete_me.py", "action": "delete", "old_text": "gone\n"},
+    ]
 
     trackers = prepare_file_edit_trackers(
         call_id="call-patch",
         tool_name="apply_patch",
         tool=None,
         workspace=tmp_path,
-        params={"patch": patch},
+        params={"edits": edits},
     )
 
     assert [tracker.display_path for tracker in trackers] == [
@@ -118,7 +113,7 @@ def test_apply_patch_prepares_trackers_for_each_touched_file(tmp_path: Path) ->
     existing.write_text("new\nkeep\n", encoding="utf-8")
     delete_me.unlink()
 
-    events = [build_file_edit_end_event(tracker, {"patch": patch}) for tracker in trackers]
+    events = [build_file_edit_end_event(tracker, {"edits": edits}) for tracker in trackers]
     by_path = {event["path"]: event for event in events}
     assert (by_path["src/new.py"]["added"], by_path["src/new.py"]["deleted"]) == (1, 0)
     assert (by_path["src/existing.py"]["added"], by_path["src/existing.py"]["deleted"]) == (1, 1)
@@ -135,12 +130,9 @@ def test_apply_patch_dry_run_does_not_prepare_file_edit_trackers(tmp_path: Path)
         workspace=tmp_path,
         params={
             "dry_run": True,
-            "patch": """*** Begin Patch
-*** Update File: file.txt
-@@
--old
-+new
-*** End Patch""",
+            "edits": [
+                {"path": "file.txt", "action": "replace", "old_text": "old", "new_text": "new"}
+            ],
         },
     )
 
@@ -221,14 +213,8 @@ def test_streaming_apply_patch_tracker_emits_live_counts_per_file(tmp_path: Path
             "call_id": "call-patch",
             "name": "apply_patch",
             "arguments_delta": (
-                '{"patch":"*** Begin Patch\\n'
-                '*** Update File: src/existing.py\\n'
-                '@@\\n'
-                '-old\\n'
-                '+new\\n'
-                ' keep\\n'
-                '*** Add File: src/new.py\\n'
-                '+fresh\\n'
+                '{"edits":[{"path":"src/existing.py","action":"replace","old_text":"old","new_text":"new"}'
+                ',{"path":"src/new.py","action":"add","new_text":"fresh"}]}'
             ),
         })
 
@@ -255,9 +241,7 @@ def test_streaming_apply_patch_tracker_skips_dry_run(tmp_path: Path) -> None:
             "call_id": "call-patch",
             "name": "apply_patch",
             "arguments_delta": (
-                '{"dry_run":true,"patch":"*** Begin Patch\\n'
-                '*** Add File: dry.md\\n'
-                '+preview\\n'
+                '{"dry_run":true,"edits":[{"path":"dry.md","action":"add","new_text":"preview"}]}'
             ),
         })