refactor: rename ProtoTauriIPC to ProtoGossamerIPC, clean Tauri references

Complete Tauri-to-Gossamer migration for protocol types:
- Rename ProtoTauriIPC variant to ProtoGossamerIPC across CladeBrowserModel,
  CladeBrowserEngine (60+ usages), and display label
- Update CladeBrowserEngine comment to reference Gossamer instead of Tauri
- Mark legacy tauri:// URI handler in RuntimeResolver as DEPRECATED
- Obj.magic audit: no actual usage found (all references are comments
  documenting the banned pattern or Hypatia detection rules)
- Build verified: 743 modules compiled cleanly

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

Author: hyperpolymath