feat(cli): integrate ctxcn toolkit into cvmi and stabilize test suite

[aphrodoe]

Description

This PR fully integrates ctxcn natively into the core cvmi binary as the cvmi cn sub-command, centralizing the ContextVM ecosystem tooling while systematically patching bugs across test environment.

Major Changes

• Unified Tooling: Ported the ctxcn ecosystem natively into cvmi under src/cn/ keeping schemas strongly-typed.
• Sub-commands Scaffolded: Implemented and wired cvmi cn init, cvmi cn add, and cvmi cn update capabilities directly into the root src/cli.ts routing layer.

Testing & Architecture Stability

• Compatibility Patch: Fixed systemic ERR_UNKNOWN_FILE_EXTENSION bugs across the test suite (remove.test.ts, add.test.ts) by natively executing subprocess spawns structurally via ${process.execPath} ${TSX_PATH}.
• Timeouts Hardened: Extrapolated a vitest.config.ts enforcing a global 20s test boundary to safely accommodate cross-platform tsx bootup latency.

Documentation

• Explicitly documented the cvmi cn command ecosystem structure within README.md.
• Appended modular lifecycle notes detailing cvmi cn hierarchy mapping logic within AGENTS.md.

Testing Verification

• All 158 tests successfully pass via pnpm test.
• Confirmed zero regression test-flakes.

[ContextVM-org]

Looking good. Just add a changeset with this change before we can merge it