Adopt the shared Foundation Dagger guard

[hseshadr]

TL;DR: Pin the central Foundation Lego at 068c3c08 and bind the caller snapshot to the exact public commit before any product or security work.

What changed:

• require ci(commit_sha) and run Foundation source binding plus guard first
• consolidate push, pull request, manual, and Monday security ingress into the protected Dagger workflow
• keep the source-free npm OIDC release candidate and publisher byte-identical
• document the current central npm-publisher gap and ownership boundary

Verification:

• Python quality: Ruff, format, strict mypy, Xenon A, 15 tests
• Product gate: 139 tests, 100% core coverage, 2 Playwright tests, build
• Dagger: develop/schema, quality, dependency audit, actionlint workflow audit, 57-commit secret scan
• Independent review: Ready Yes, no findings