fix(patch): gate 'did you mean?' to no-match + extend to v4a/skill_manage

Follow-ups on top of @teyrebaz33's cherry-picked commit:

1. New shared helper format_no_match_hint() in fuzzy_match.py with a
   startswith('Could not find') gate so the snippet only appends to
   genuine no-match errors — not to 'Found N matches' (ambiguous),
   'Escape-drift detected', or 'identical strings' errors, which would
   all mislead the model.

2. file_tools.patch_tool suppresses the legacy generic '[Hint: old_string
   not found...]' string when the rich 'Did you mean?' snippet is
   already attached — no more double-hint.

3. Wire the same helper into patch_parser.py (V4A patch mode, both
   _validate_operations and _apply_update) and skill_manager_tool.py so
   all three fuzzy callers surface the hint consistently.

Tests: 7 new gating tests in TestFormatNoMatchHint cover every error
class (ambiguous, drift, identical, non-zero match count, None error,
no similar content, happy path). 34/34 test_fuzzy_match, 96/96
test_file_tools + test_patch_parser + test_skill_manager_tool pass.
E2E verified across all four scenarios: no-match-with-similar,
no-match-no-similar, ambiguous, success. V4A mode confirmed
end-to-end with a non-matching hunk.

tools/patch_parser.py

@@ -290,10 +290,16 @@ def _validate_operations(
                 )
                 if count == 0:
                     label = f"'{hunk.context_hint}'" if hunk.context_hint else "(no hint)"
-                    errors.append(
+                    msg = (
                         f"{op.file_path}: hunk {label} not found"
                         + (f" — {match_error}" if match_error else "")
                     )
+                    try:
+                        from tools.fuzzy_match import format_no_match_hint
+                        msg += format_no_match_hint(match_error, count, search_pattern, simulated)
+                    except Exception:
+                        pass
+                    errors.append(msg)
                 else:
                     # Advance simulation so subsequent hunks validate correctly.
                     # Reuse the result from the call above — no second fuzzy run.
@@ -537,7 +543,13 @@ def _apply_update(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
                             error = None
                 
                 if error:
-                    return False, f"Could not apply hunk: {error}"
+                    err_msg = f"Could not apply hunk: {error}"
+                    try:
+                        from tools.fuzzy_match import format_no_match_hint
+                        err_msg += format_no_match_hint(error, 0, search_pattern, new_content)
+                    except Exception:
+                        pass
+                    return False, err_msg
         else:
             # Addition-only hunk (no context or removed lines).
             # Insert at the location indicated by the context hint, or at end of file.