feat: DeepSeek API integration + Whale lift (hooks, tool repair, MCP permissions, token tracking)

DeepSeek API:
- @ai-sdk/deepseek provider replaces openai-compatible for deepseek-* models
- Token tracking: cache_hit/reasoning tokens flow API → DB → WS frames → UI
- thinking effort levels (off/low/medium/high/xhigh/max) via AGENTS.md frontmatter
- V4 models: deepseek-v4-flash, deepseek-v4-pro
- Wired for both chat and coder panes

Whale lifts:
- Tool input repair (schema-based type coercion, markdown link unwrapping)
- Hooks system (6 lifecycle events, shell exec, JSON stdin/stdout contract)
- Per-MCP-server permissions (allow/ask/deny)
- token tracking UI (cache N, think N in message stats line)

Infra:
- New DB columns: messages.cache_tokens, messages.reasoning_tokens
- New WS frame fields: cache_tokens, reasoning_tokens on message_complete
- coder provider snapshot merges DeepSeek models alongside llama-swap

apps/coder/src/config.ts

@@ -50,6 +50,8 @@ const ConfigSchema = z.object({
   // only reaped after it's been untouched this long (avoids sweeping a dir mid
   // ensureSessionWorktree create). 1h default.
   ORPHAN_WORKTREE_GRACE_MS: z.coerce.number().int().positive().default(3_600_000),
+  DEEPSEEK_API_KEY: z.string().optional(),
+  DEEPSEEK_BASE_URL: z.string().url().default('https://api.deepseek.com'),
 });
 
 export type Config = z.infer<typeof ConfigSchema>;