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/file_operations.py

@@ -741,10 +741,8 @@ class ShellFileOperations(FileOperations):
         if error or match_count == 0:
             err_msg = error or f"Could not find match for old_string in {path}"
             try:
-                from tools.fuzzy_match import find_closest_lines
-                hint = find_closest_lines(old_string, content)
-                if hint:
-                    err_msg += "\n\nDid you mean one of these sections?\n" + hint
+                from tools.fuzzy_match import format_no_match_hint
+                err_msg += format_no_match_hint(err_msg, match_count, old_string, content)
             except Exception:
                 pass
             return PatchResult(error=err_msg)