Execute dynamic tools through llm-providers

[stackbilt-admin]

Summary

• routes runtime dynamic-tool execution through buildLLMProviderFactory(env)
• removes direct env.ai.run() and raw Groq fetch inference from dynamic-tools.ts
• preserves dynamic-tool executor choices by mapping gpt_oss, workers_ai, and groq to their configured provider models
• adds focused provider-boundary tests for dynamic-tool execution and availability errors

Refs #24. This removes another public raw-provider inference surface; the broader epic remains open for router/probe/composite/scheduled cleanup.

Validation

• npm run typecheck
• npx vitest run tests/dynamic-tools-provider.test.ts tests/claude-provider.test.ts
• npm test
• npx charter validate
• git -c core.whitespace=blank-at-eol,blank-at-eof,space-before-tab,cr-at-eol diff --check
• npm pack --dry-run