[jimmyplup]

Adds Synap (by Linkrra) as a new OpenAI-compatible LLM provider.

Synap is a hosted inference API (https://pool.linkrra.com/v1) where the synap-v1 model auto-routes each request to the cheapest model that can handle it (tools, code, or reasoning), billed at the price of whichever model actually ran. A free daily tier (100K tokens, 50 requests on Qwen3 Coder 30B) is available with no card, via Google sign-in at https://synap.linkrra.com.

Follows the same pattern as the recently-merged Tensorix provider (#11184):

• New core/llm/llms/Synap.ts (thin OpenAI subclass)
• Registered in core/llm/llms/index.ts, core/llm/autodetect.ts, core/control-plane/schema.ts
• Added to packages/openai-adapters types/index
• Added to the VS Code extension config schema and GUI provider list
• New docs page under docs/customize/model-providers/more/synap.mdx

Live endpoint verified: curl https://pool.linkrra.com/v1/models returns synap-v1 (200).

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