Serialize execute_code sessions per bot

[MaxBittker]

Summary

• run execute_code in a per-bot FIFO while allowing different bots to proceed concurrently
• stop timed-out or cancelled programs from starting new SDK calls
• keep the bot lock until SDK calls that already started have settled
• use a request-scoped console so concurrent sessions do not overwrite process globals, while routing SDK diagnostics away from MCP stdout
• preserve TypeScript bodies, bounded logs, partial error output, and the terminal world-state snapshot

Deliberately omitted from #44

No structured inspect/query/action tools, session-health metadata, resource abstraction, connection-manager rewrite, or separate output framework. This is the smallest slice that prevents agent programs from interleaving mutations.

Validation

• bun run check
• 7 focused MCP execution/FIFO tests pass
• MCP TypeScript check passes
• MCP initialize handshake passes over stdio
• generated sdk/API.md is refreshed for already-merged Fix agent state telemetry and browser action contracts #45 (17-line post-merge drift fix)

Boundary

execute_code remains trusted, unsandboxed execution. CPU-bound synchronous code cannot be pre-empted. An SDK call that already started cannot be force-aborted, so the next same-bot session intentionally waits for it to settle.

Supersedes #44.