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

.env.example

@@ -20,6 +20,12 @@ SEARXNG_URL=http://100.114.205.53:8888
 # with FAST_MODEL when unset.
 # TASK_MODEL_URL=http://100.90.172.55:7995
 
+# DeepSeek API key. When set, models with IDs starting with 'deepseek-'
+# (e.g. deepseek-chat, deepseek-reasoner, deepseek-v4-flash) route through
+# DeepSeek's API instead of llama-swap. Requires a DeepSeek Platform API key.
+# DEEPSEEK_API_KEY=sk-...
+# DEEPSEEK_BASE_URL=https://api.deepseek.com
+
 # v1.13.15-tools: BOOCODE_TOOLS narrows the tool whitelist sent to the LLM.
 # Unset (default) → all tools (~21k schema). Useful primarily for single-purpose
 # sessions where the model only needs read-only filesystem access.