Non-network errors seen in logs:

- AI_APICallError (402 deactivated_workspace)

- AI_APICallError (500 server_error)

- AI_LoadAPIKeyError / OpenAI API key is missing

- ProviderInitError

- ConfigInvalidError

- ProviderAuthOauthCallbackFailed

- NotFoundError

- EditBuffer is destroyed

- Add getUsage() to fetch OAuth account status and health
- Add fetchAnthropicUsage() to fetch Claude Max rate limits from Anthropic API
- Add GET /auth/usage endpoint to expose usage data

- Add DialogAuthUsage component with rate limit visualization
- Display Anthropic 5-hour and 7-day limits with progress bars
- Show OAuth account status, cooldown state, and request counts
- Add button in sidebar to open the dialog

- Add AuthUsageCommand to display rate limit info in terminal
- Show account status, cooldown state, and request counts
- Display Anthropic rate limits when available

The AI SDK's convertToModelMessages() does not accept 'step-start' as a valid
UIMessagePart type. This caused AI_InvalidPromptError during session compaction.

- Remove step-start from being added to UIMessage parts
- Simplify the filter since step-start is no longer included
- Fixes compaction breaking sessions with context overflow

…ashboard

## Summary
Implements comprehensive multi-account OAuth support with automatic rate limit
rotation, manual account switching, and a new Settings menu for the desktop app.

## Features

### Multi-Account OAuth Rotation (Backend)
- Add `Auth.OAuthPool.setActive()` to manually switch active OAuth account
- Add `Auth.OAuthPool.snapshot()` returns `activeID` for credential selection
- Update `rotating-fetch.ts` to prefer `activeID` while keeping auto-rotation
- Update `fetchAnthropicUsage()` to respect `provider.active[namespace]`
- Update `getAccounts()` to correctly identify active account

### API Endpoints
- Add `POST /auth/active` endpoint to switch active OAuth account
- Returns updated `anthropicUsage` for immediate UI updates

### Desktop App - Settings Menu
- New `DialogSettings` component with tabbed interface
- **Providers Tab**: View connected providers, add new providers with search
- **Provider Detail View**: Account list, usage stats, switch functionality
- **About Tab**: GitHub, docs, Discord links, keyboard shortcuts
- Inline provider search without leaving settings context

### Desktop App - Context Panel
- Add Anthropic Rate Limits section in session context panel
- Shows 5-hour, weekly (all models), weekly (sonnet) usage bars
- Account switch buttons when multiple accounts configured
- Only visible when current session uses Anthropic provider

### CLI Enhancements
- `opencode auth usage`: Shows individual usage per OAuth account
- `opencode auth switch`: Interactive command to switch active account
- `opencode auth list`: Shows account count per provider
- All provider lists now sorted alphabetically

## Technical Details

### Files Changed
- `packages/opencode/src/auth/index.ts`: Core OAuth pool functions
- `packages/opencode/src/auth/rotating-fetch.ts`: Credential selection
- `packages/opencode/src/server/server.ts`: API endpoint
- `packages/opencode/src/cli/cmd/auth.ts`: CLI commands
- `packages/app/src/components/dialog-settings.tsx`: New settings UI
- `packages/app/src/components/session/session-context-tab.tsx`: Context panel
- `packages/app/src/pages/layout.tsx`: Settings button integration

### Auto-Rotation Flow
1. Request uses `activeID` (manually selected or first available)
2. On 429 rate limit → account gets cooldown, moved to back
3. Next request automatically uses next available account
4. Manual switch via UI/CLI updates `provider.active[namespace]`

### Anthropic Usage Stats
Currently only Anthropic provides OAuth usage statistics.
Other providers show multi-account switching but no usage bars.
Contributions welcome for additional provider support.