Summary

Add a protocol-level ACP conformance suite for ACPX with a data-driven runner and CI/nightly coverage.

This establishes a stable, deterministic baseline for core ACP behavior and makes it straightforward to run the same profile against real adapters via --agent-command.

Why

ACPX currently relies on integration tests and manual checks to catch ACP regressions. What was missing is a protocol-focused contract layer that is deterministic, adapter-agnostic, and easy to extend.

This PR adds that missing layer.

Changes

• Add conformance/spec/v1.md (normative v1 contract)
• Add conformance/profiles/acp-core-v1.json (required-case profile)
• Add 20 core conformance cases under conformance/cases/*.json
• Add data-driven runner at conformance/runner/run.ts
  • JSON-defined steps execution (new_session, prompt, prompt_background, await_background, cancel, sleep)
  • JSON-defined checks evaluation
  • per-case permission_mode override support
  • JSON report output support
• Add conformance/README.md usage and model docs
• Add conformance:run script in package.json
• Integrate CI smoke run in .github/workflows/ci.yml
• Add nightly workflow .github/workflows/conformance-nightly.yml
  • full mock-profile run + artifacts
  • optional real-adapter smoke matrix (repo var / manual dispatch)

Validation

Local verification completed:

• pnpm run conformance:run (20/20 passed)
• pnpm run typecheck
• pnpm run lint
• pnpm run check:docs

Scope

Included:

• ACP core lifecycle and baseline error semantics
• deterministic protocol conformance baseline using test/mock-agent.ts

Not included in this PR:

• provider-specific UX assertions
• performance benchmarking
• unstable ACP method coverage