fix(installer): retry git ops + reject placeholder api_key + sync public configs

User hit two bugs in production:
1. uclaude_install.sh ERROR: Command failed at line 82 — gitea returned
   transient HTTP 502 to `git fetch`, `2>/dev/null` masked stderr but
   ERR trap fired with cryptic message.
2. After install, claude model picker showed only 5 models (built-in
   defaults) instead of 19. Root cause: load_config() fell back to the
   PUBLIC sanitized patcher.config.json (api_key='YOUR_API_KEY') after
   remote fetch failed → claude API auth broken → custom models invisible.

Fixes:

claude/uclaude_install.sh:
- New retry_git() helper: 3 attempts, 5s backoff, loud diagnostic
- Existing-clone branch: retry_git wraps `git fetch` AND `git reset`
- Fallback: if fetch fails 3x on existing clone, nuke and re-clone fresh
  (incremental fetch breaks more often than full clone on flaky gitea)
- Secondary fetch (before updater): tolerates failure with `|| true`
  (we already have a working clone)

claude/uclaude_updater.py:
- _config_is_usable() guard: rejects {"api_key": "YOUR_API_KEY"} etc.
- load_config() retries remote 3x with backoff before falling back
- Removed local-file fallback (was loading public sanitized = bait)
- Cache-only fallback now (from previous successful fetch)

Public configs synced from canonical (api_key sanitized, models list
fully refreshed):
- claude/patcher.config.json: 17 → 19 models (+gpt-5.5, +gemini-3.1-pro etc)
- codex/codex_config.json: 4 → 5 models (+gpt-5.5)
- gemini/gemini_config.json: refreshed
- target_version: 2.1.112 → 2.1.119

Tests: tests/test_installer_robustness.py — 6 new GREEN guards.
Total: 196 → 207 GREEN.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

gemini/gemini_config.json

@@ -19,5 +19,5 @@
   "telemetry_enabled": false,
   "npm_package": "@google/gemini-cli",
   "npm_registry": "https://npm.sensey24.ru",
-  "_note": "Production config (with real api_key) lives in PRIVATE unlimitedcoding-config repo. This file is a template only."
+  "_note": "Production api_key lives in PRIVATE unlimitedcoding-config repo."
 }