fix: preserve old sessions after ZCode setup

[vitry]

Summary

• stop ZCode from writing the Codex host-owned hide_spawn_agent_metadata = false override that changes the reserved collaboration.spawn_agent schema and breaks resumed sessions
• keep the managed zcode-rescue Role, migrate ownership-proven numeric-v1 installs to the exact "1.0.0" receipt in one setup reconciliation, and harden transaction rollback/recovery
• make Role/setup changes ready in one run while preserving the separate writable-root bootstrap restart boundary
• package bilingual receipt-gated manual cleanup guidance for uninstall residuals without adding an uninstall command or hook

Compatibility and safety

• fresh/current installs never edit, compare, or restore the host spawn-metadata flag
• only an exact numeric-v1 receipt + target config + exact Role registration + Role digest can authorize deletion of the target-layer legacy false leaf
• true, project-layer, foreign, malformed, and unproven values fail closed
• receipt/Role/config activation is verified before commit; rollback writes are reread and proven before recovery evidence is removed
• existing numeric-v1 transaction journals remain recoverable
• named agent_type: zcode-rescue and the proven generic pre-child fallback are unchanged
• marketplace/plugins/zcode/ is intentionally unchanged; regenerate/repackage only after merge

Verification

• npm run check:line-endings
• npm run lint
• npm run typecheck
• npm test — 1115 passed, 3 authenticated opt-in skips; marketplace snapshot build 2/2 passed
• npm run test:qualified — 6 passed, 3 explicit opt-in skips
• npm pack --dry-run --json — 147 files, including docs/manual-uninstall.md
• git diff --check origin/main...HEAD
• independent spec, rollback/code-quality, and ../codex-plugin-cc design-conflict reviews: no remaining Critical/Important findings