Expand model providers and harden the runtime

[JaviChulvi]

Summary

• add first-class OpenAI-compatible, OpenRouter, Anthropic, Bedrock, and Gemini providers alongside OpenAI, DeepSeek, and local
• centralize provider profiles, capabilities, structured-action parsing, error classification, fallback accounting, and context budgeting
• add native async provider execution and cancellation-safe fallback behavior while preserving sync-only custom-client compatibility
• harden shell execution, sensitive file reads, durable memory, provider diagnostics, and configuration redaction
• add versioned trace replay, deterministic offline evaluations, package-wide type checking, and provider setup documentation

Why

Provider integration and action handling had grown across provider-specific paths, which made fallback behavior, async execution, capability checks, and extension compatibility harder to reason about. Safety checks also needed stronger runtime enforcement around shell processes, file reads, memory persistence, and diagnostic output.

This change keeps provider details inside the LLM boundary, makes the shared orchestration path explicit, and preserves the original custom-provider factory contract.

Provider configuration

The implementation follows the existing Chulk environment model and documents the exact precedence for:

• CHULK_LLM_PROVIDER, CHULK_MODEL, and CHULK_LLM_FALLBACK_PROVIDERS
• OpenAI, DeepSeek, local, OpenRouter, Anthropic, Bedrock, and Gemini key aliases
• provider-specific base URLs, including explicit Bedrock and generic OpenAI-compatible endpoints
• individual SDK extras and the aggregate providers extra

Validation

• python -m pytest -q — 677 passed
• python -m ruff check chulk examples scripts
• python -m mypy chulk typing_tests — 95 source files
• python -m compileall -q chulk examples scripts
• python scripts/check_docs.py
• clean wheel build and clean-virtualenv installation smoke
• credential-free SDK quickstart and repository-review example

Provider adapter tests use injected fake SDK clients and make no live billable calls. Live keys, endpoints, model identifiers, account entitlements, quotas, and billing still require owner validation before merge.