fix: prevent dictionary false positives + add tunnel-doctor WSL/Go findings

transcript-fixer:
- Add common_words.py safety system (blocks common Chinese words from dictionary)
- Add --audit command to scan existing dictionary for risky rules
- Add --force flag to override safety checks explicitly
- Fix substring corruption (产线数据→产线束据, 现金流→现现金流)
- Unified position-aware replacement with _already_corrected() check
- 69 tests covering all production false positive scenarios

tunnel-doctor:
- Add Step 5A: Tailscale SSH proxy silent failure on WSL
- Add Step 5B: App Store vs Standalone Tailscale on macOS
- Add Go net/http NO_PROXY CIDR incompatibility warning
- Add utun interface identification (MTU 1280=Tailscale, 4064=Shadowrocket)
- Fix "Four→Five Conflict Layers" inconsistency in reference doc
- Add complete working Shadowrocket config reference

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

transcript-fixer/scripts/fix_transcription.py

@@ -31,6 +31,7 @@ from __future__ import annotations
 from cli import (
     cmd_init,
     cmd_add_correction,
+    cmd_audit,
     cmd_list_corrections,
     cmd_run_correction,
     cmd_review_learned,
@@ -89,6 +90,8 @@ def main() -> None:
     elif args.add_correction:
         args.from_text, args.to_text = args.add_correction
         cmd_add_correction(args)
+    elif getattr(args, 'audit_dictionary', False):
+        cmd_audit(args)
     elif args.list_corrections:
         cmd_list_corrections(args)
     elif args.review_learned: