Immutable plugin generations

The plugin installer never edits an active payload. It stages a complete content-addressed generation, verifies its Ed25519-signed canonical manifest and every signed target receipt against a separate trust store, then atomically switches current.

The manifest records the generation, complete file inventory, modes, content hashes, target payload modes, required stable entrypoints, canonical skill-index receipt, source commit/tree state, and external gitlink commit pins. A generation is active only when signature, trust, provenance, payload, index, and receipt verification succeeds.

current points to the active payload and index as one transaction. previous preserves the last certified generation for rollback. Hardcoded version directories are forbidden because they bypass content verification and become stale after upgrades.

The host, generated-agent, and mobile index projections are byte-identical and use the shared deterministic selector. See Signing, indexes, and receipts for the full trust and parity contract.

Verify without mutation:

node scripts/install-plugin-generation.js --verify