Draft: native pipeline.open proof

[thejackshelton]

Summary

This draft captures the current native-testing direction for pipeline.open(...) so it can be reviewed in the witness repo, but it is not merge-ready yet.

It adds:

• pipeline.open(...) receipt plumbing and app-session evidence
• macOS Accessibility and iOS XCTest adapter sketches
• focused fake-adapter and adapter command-construction tests
• a skipped-by-default live macOS proof using a local AppKit demo

Merge blockers

• Blocker: macOS screenshots capture the entire desktop, not the app. src/adapters/macos-ax.ts uses screencapture -x, and test/platform-adapters.test.ts locks that in. The saved proof screenshot includes unrelated windows, so this is both weak evidence and a privacy/security issue.
• Blocker: generated Xcode output is inside the proposed untracked tree. pnpm run check fails on test/support/macos-xctest-bridge/.build/**, and .gitignore does not exclude it. That violates the generated-output rule.
• Blocker: Node command execution is exported from the package root via src/index.ts and src/adapters/command.ts. Existing host APIs live under documented CLI boundaries; this makes a Node-only command runner part of the importable library surface.
• Major: the live native proof is skipped by default. pnpm run test test/native-macos-live.test.ts reports 1 skipped test, so CI would not prove the native path unless a separate gated job is added.
• Minor: src/types.ts says “seven-key context,” but the context still has six top-level keys; this change only adds pipeline.open(...).

Verification from the local evaluation

• Passed: pnpm run test test/pipeline-open.test.ts test/platform-adapters.test.ts test/witness.test.ts — 3 files, 24 tests.
• Passed: pnpm run build.
• Failed: pnpm run check because generated native .build output is scanned.
• Failed independently: pnpm exec tsc --noEmit also reports existing unrelated errors in src/cli/cdp-browser.ts.
• Skipped by default: pnpm run test test/native-macos-live.test.ts — 1 skipped test.

External usage context checked with grep MCP

• xcrun simctl launch and xcrun simctl io booted screenshot are common simulator primitives in native test tooling.
• JXA via osascript -l JavaScript is a known macOS automation fallback.
• These patterns support the direction, but they do not resolve the repo-specific host-boundary, evidence-quality, generated-output, and CI-proof blockers above.