MCP Runtime structural upgrade

[ethan-huo]

Objective

Implement the accepted MCP Runtime structural upgrade in docs/specs/mcp-runtime-upgrade.md.

This is the tracking issue for the complete dependency graph. Implementation belongs in sub-issues; do not turn this issue into a second specification.

Frozen product semantics

• The CLI Adapter is short-lived and never owns MCP transports or credentials.
• An ordinary Call with unusable credentials returns reauth-required; it never starts authentication.
• Only explicit mcpx @refresh may start or join an Authentication Flow.
• CLI disconnect cancels only its own Call and never evicts a healthy shared session.
• Declared Registry, Credential Store, Schema Cache, and Active State stay separate.

Completion

• Every sub-issue is closed through its own acceptance criteria.
• Issue bug: parallel cf-api execute processes spin at ~100% CPU after caller exits #16 is reproduced and closed through deterministic local process-level coverage.
• Final independent review finds no unresolved correctness or lifecycle defects.
• No real OAuth, Cloudflare, PostHog, or other remote MCP endpoint is required.

[ethan-huo]

The MCP Runtime structural upgrade is complete. All dependency issues #19, #20, #10, #18, #21, #22, #16, and #23 are closed. The accepted spec and ADRs are implemented, the original process/CPU symptom is covered by deterministic local five-process HTTP acceptance, and final independent review found no unresolved blocker. Final gate: 120 tests, typecheck, format, pinned cancellation prototype evidence, and diff check all pass; no remote OAuth or MCP was accessed.

[ethan-huo]

Closing the parent after every dependency and final acceptance gate completed.

[ethan-huo]

The structural Runtime upgrade is now publicly released as v0.10.2. PR #24 contains the accepted architecture; PR #25 makes the installed artifact self-contained; PR #26 makes the cross-process single-flight evidence deterministic.

Final gates: 120/120 tests, typecheck, formatting, build, GitHub CI, Release workflow, anonymous asset download/hash verification, and isolated public-artifact daemon dogfood.