fix(testbox): preserve complete source snapshots (#138404)

fix(testbox): preserve complete source snapshots (#138404)

Freeze policy-selected raw source into the existing Git-bundle path and verify filesystem bytes, symlink targets, executable flags, and producer-owned deletions before executing Testbox proof. Remove the unverified remote auto-commit and fingerprint the actual source-owner modules.

Closes #138153. Verified native checksum-full recovery against the complete source hash; 284/284 Linux owner tests passed with an unchanged candidate manifest. Native openrsync deletion of ignored runtime directories remains a separate limitation.