refactor(mcp): converge runtime lifecycle ownership

[limityan]

Summary

• encapsulate MCP process start/stop/status/connection access in MCPServerRuntimeState instead of exposing mutable process handles across the Services/Core boundary
• split external ephemeral install/retirement logic from persistent MCP lifecycle while keeping product publication, workspace scope, and readiness in Core
• remove duplicate provider-neutral policy assertions from the heavy Core test target and reuse the existing Services owner contract coverage

Architecture and behavior

• Services owns registry/process/connection-pool/catalog lifecycle; Core injects typed local/remote start paths and publishes product-facing tools/events only after external retirement/start-token checks
• Started always carries a live connection; invalid context or a missing post-start connection fails explicitly
• local and remote restart now share the complete Core stop_server -> start_server lifecycle, preventing stale connection-pool, ToolRegistry, catalog, or listener references
• public Core compatibility imports remain unchanged

Dependency and CI impact

• no Cargo dependency, feature, lockfile, workflow, job, or CI test-step changes
• no product-full expansion; owner verification uses only bitfun-services-integrations --no-default-features --features mcp
• 7 files, 1 commit, 645 insertions / 600 deletions

Verification

• cargo test -p bitfun-services-integrations --no-default-features --features mcp --test mcp_contracts (41 passed)
• cargo test -p bitfun-core --lib service::mcp::server::manager::tests -- --nocapture (3 passed)
• cargo check -p bitfun-core --lib
• git diff --check gcwing/main...HEAD
• isolated adversarial review completed; restart connection split, optional-success state, and path-before-idempotency findings were fixed and re-reviewed with no remaining P0-P2

Local-only artifacts

The implementation spec and plan under docs/superpowers/** remain untracked locally and are not part of this PR.