Selective fixes from PR #35: Model-specific rate limits & robustness improvements (#37)

* feat: apply local user changes and fixes

* ;D

* Implement OpenAI support, model-specific rate limiting, and robustness fixes

* docs: update pr title

* feat: ensure unique openai models endpoint

* fix: startup banner alignment and removed duplicates

* feat: add model fallback system with --fallback flag

* fix: accounts cli hanging after completion

* feat: add exit option to accounts cli menu

* fix: remove circular dependency warning for fallback flag

* feat: show active modes in banner and hide their flags

* Remove OpenAI compatibility and fallback features from PR #35

Cherry-picked selective fixes from PR #35 while removing:
- OpenAI-compatible API endpoints (/openai/v1/*)
- Model fallback system (fallback-config.js)
- Thinking block skip for Gemini models
- Unnecessary files (pullrequest.md, test-fix.js, test-openai.js)

Retained improvements:
- Network error handling with retry logic
- Model-specific rate limiting
- Enhanced health check with quota info
- CLI fixes (exit option, process.exit)
- Startup banner alignment (debug mode only)

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

* banner alignment fix

* Refactor: Model-specific rate limits and cleanup deprecated code

- Remove global rate limit fields (isRateLimited, rateLimitResetTime) in favor of model-specific limits (modelRateLimits[modelId])
- Remove deprecated wrapper functions (is429Error, isAuthInvalidError) from handlers
- Filter fetchAvailableModels to only return Claude and Gemini models
- Fix getCurrentStickyAccount() to pass model param after waiting
- Update /account-limits endpoint to show model-specific limits
- Remove multi-account OAuth flow to avoid state mismatch errors

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

* fix: show (x/y) limited status in account-limits table

- Status is now "ok" only when all models are available
- Shows "(x/y) limited" when x out of y models are exhausted
- Provides better visibility into partial rate limiting

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

* docs: update CLAUDE.md with model-specific rate limiting

- Document modelRateLimits[modelId] for per-model rate tracking
- Add isNetworkError() helper to utilities section

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

---------

Co-authored-by: M1noa <minoa@minoa.cat>
Co-authored-by: Minoa <altgithub@minoa.cat>
Co-authored-by: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -106,7 +106,8 @@ src/
 
 **Multi-Account Load Balancing:**
 - Sticky account selection for prompt caching (stays on same account across turns)
-- Automatic switch only when rate-limited for > 2 minutes
+- Model-specific rate limiting via `account.modelRateLimits[modelId]`
+- Automatic switch only when rate-limited for > 2 minutes on the current model
 - Session ID derived from first user message hash for cache continuity
 - Account state persisted to `~/.config/antigravity-proxy/accounts.json`
 
@@ -147,6 +148,7 @@ src/
 **Utilities:** Shared helpers in `src/utils/helpers.js`:
 - `formatDuration(ms)` - Format milliseconds as "1h23m45s"
 - `sleep(ms)` - Promise-based delay
+- `isNetworkError(error)` - Check if error is a transient network error
 
 **Logger:** Structured logging via `src/utils/logger.js`:
 - `logger.info(msg)` - Standard info (blue)