Phase 13 milestone 50. Replaces rcp/e2e.hpp with the specification's actual end-to-end CRC (32-bit, polynomial 0xF4ACFB13, both input/output reflected) and its exact stream_id + avtp_timestamp + ACF header + payload coverage/length-adjustment rule; adds per-endpoint opt-in CRC safe mode, the safety-tagged (0x8x) compound/compound-wait/triggered request variants gated on safe-state entry, and the full per-request-stream watchdog/safe-state register set in rcp/regmap.hpp. This is the milestone the Phase 13 introduction names as "the point at which the mandatory baseline plus safe-points exist," building on v2.5.0's conditional-request taxonomy and sequencer.
See ROADMAP.md's "Done (v2.6.0)" entry under milestone 50 for full details, and PR #43 for the change itself.