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/server/src/services/system-prompt.ts

@@ -101,7 +101,7 @@ export interface PrefixFingerprint {
   has_agent_system_prompt: boolean;
   has_session_override: boolean;
   has_project_override: boolean;
-  route: 'swap' | 'sidecar';
+  route: 'swap' | 'sidecar' | 'deepseek';
 }
 
 export interface PrefixDrift {
@@ -129,7 +129,7 @@ interface ObservedInputs {
   has_agent_system_prompt: boolean;
   has_session_override: boolean;
   has_project_override: boolean;
-  route: 'swap' | 'sidecar';
+  route: 'swap' | 'sidecar' | 'deepseek';
 }
 
 interface ObserverEntry {