docs: record access v2 production migration (#57)

AGENTS.md

@@ -63,6 +63,7 @@
 - Add automated tests in proportion to behavioral risk. Block the current phase on P0 security, privacy, irreversible data, authorization, generation, bounded-resource, and rollback failures, plus P1 failures of the milestone's core user path. Record or cover P2/P3 rare environments, diagnostic detail, and minor UI edges cheaply without turning them into canary blockers unless they can cause P0 harm. Use high-repeat race runs only for a reproduced concurrency failure. For realtime media changes, also document the manual network and browser matrix used.
 - Batch validation by risk and phase: run narrow checks while iterating, and run expensive full suites, browser matrices, endurance tests, or deployment checks only at an acceptance boundary or when a relevant change invalidates prior evidence. Documentation-only or unrelated changes do not invalidate media-path evidence.
 - A dedicated deployment subagent owns each staged production deployment and verification while root/mainline continues; root supplies the exact merged SHA, artifact hash, rollback target, and acceptance list, and the deployer must not expand scope.
+- Immutable production releases must not share hard-linked dependencies or other permission-mutated files with a rollback release. Copy or reflink an independent tree, verify zero shared regular-file inodes, and only then change ownership or switch the release symlink.
 - Use comments for non-obvious rationale, invariants, protocol constraints, and workarounds; do not narrate obvious code.
 - Use WebRTC statistics and reproducible measurements for latency, bitrate, candidate type, packet loss, encode time, and quality limitations. Do not claim performance from assumptions alone.
 - Keep repository scripts and hooks cross-platform, deterministic, fast, and runnable in CI. A hook must call a tracked script rather than hide project logic in machine-local configuration.