Add major model providers (Western + all major Chinese)

[YASSERRMD]

Multi-provider support

ClawForge is no longer effectively OpenRouter-only. Adds a generic OpenAI-compatible client, a native Anthropic client, and a catalog covering 24 providers wired up from environment variables.

Runtime (backend/planner/src/providers/)

• openai_compatible.rs — generic /chat/completions client (covers OpenAI, Gemini, Mistral, xAI, Groq, Together, Fireworks, Perplexity, Cohere, and every catalog Chinese provider).
• anthropic.rs — native Anthropic Messages API client.
• catalog.rs — ProviderInfo catalog + register_from_env, with Region/Wire metadata and a needs_residency_review() helper.

Providers covered

Global/Western: OpenRouter, OpenAI, Anthropic, Google Gemini, Mistral, xAI Grok, Groq, Together, Fireworks, Perplexity, Cohere, Ollama (local).
Chinese: DeepSeek, Alibaba Qwen (DashScope), Zhipu GLM, Moonshot/Kimi, Baidu ERNIE, MiniMax, Tencent Hunyuan, 01.AI Yi, StepFun, Baichuan, iFlytek Spark, SenseTime SenseNova.

Wiring & docs

• cli serve registers every provider whose API key is set in the env.
• .env.example lists all provider keys; new docs/model-providers.md documents them, including data-residency notes for government use.

Build fixes (pre-existing, unblock the runtime build)

• executor: import Capabilities (the CLI/runtime did not compile on main without this).
• cli: enable the tower-http limit feature used by RequestBodyLimitLayer.

Verification

• cargo test -p clawforge-planner — passing (incl. catalog tests; unique ids, Chinese coverage, env registration).
• cargo build -p clawforge-cli — now builds.