⬆️ feat: upgrade tunnel-doctor to v1.2.0 with Layer 4 SSH ProxyCommand diagnostics

Add fourth conflict layer: SSH ProxyCommand double tunneling causing
intermittent git push/pull failures when Shadowrocket TUN is active.

Structural improvements per skill best practices:
- Eliminate content duplication between SKILL.md and reference
- Rename proxy_fixes.md → proxy_conflict_reference.md for clarity
- Trim SKILL.md from 534 to 487 lines (under 500 limit)
- Shorten YAML description from 910 to 661 characters
- Fix "apply all four" listing 5 items (separate anti-pattern)
- Clarify Layer 4's relationship to Tailscale theme

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -212,7 +212,7 @@ This applies when you change ANY file under a skill directory:
 33. **meeting-minutes-taker** - Transform meeting transcripts into structured minutes with multi-pass generation, speaker quotes, and iterative human review
 34. **deep-research** - Generate format-controlled research reports with evidence mapping, citations, and multi-pass synthesis
 35. **competitors-analysis** - Evidence-based competitor tracking and analysis with source citations (file:line_number format)
-36. **tunnel-doctor** - Diagnose and fix Tailscale + proxy/VPN route conflicts on macOS with WSL SSH support
+36. **tunnel-doctor** - Diagnose and fix Tailscale + proxy/VPN conflicts (four layers: route, HTTP env, system proxy, SSH ProxyCommand) on macOS with WSL SSH support
 37. **windows-remote-desktop-connection-doctor** - Diagnose AVD/W365 connection quality issues with transport protocol analysis and Windows App log parsing
 
 **Recommendation**: Always suggest `skill-creator` first for users interested in creating skills or extending Claude Code.