Add fuzzy string matching and dedupe

[JE-Chen]

Dependency-light data batch (approved under 批准全部). Full layers + tests + EN/Zh v40 docs + README.

Feature (utils/fuzzy, stdlib default + optional rapidfuzz)

• fuzzy_ratio (0..1 similarity), fuzzy_best_match (closest of a list, score+index, or None below cutoff), fuzzy_matches (top-N sorted), fuzzy_dedupe (collapse near-duplicates, keep first). Robust to OCR/UI-copy noise — act on "the button that looks like Submit".
• Default backend is stdlib difflib — zero extra deps, so the feature (and its tests) run everywhere including the headless quality.yml job. The optional [fuzzy] extra adds rapidfuzz for speed; scores are normalised to 0..1 either way so callers never depend on the backend (BACKEND names the active one). ignore_case (default true) + score_cutoff.
• Executor AC_fuzzy_ratio / AC_fuzzy_best_match / AC_fuzzy_dedupe (choices/items as list or builder JSON string); MCP ac_fuzzy_*; Builder under Data.

Verification

• 11 tests pass (ratio bounds/identity/case, best-match closest + cutoff-None, matches sorted+limited, dedupe collapse + keep-distinct, executor round-trip, wiring, facade). Assertions check ordering/thresholds, not backend-specific floats. ruff clean; radon no CC≥C; bandit clean; PySide6-free.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 39 complexity · 0 duplication

Metric	Results
Complexity	39
Duplication	0

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud