[SoundMatt]

Summary

Implements ROADMAP.md milestone 51 ("Remaining Endpoint Types — LIN, CAN
(incl. CAN XL), ISELED, MDIO, Wakeup Control", v2.7.0), the last endpoint-type
milestone before the already-decided v2.8.0 fragmentation no-go and Phase
14's power/watchdog rebuild.

• include/rcp/lin.hpp (ep_type 0x06): LIN commander as a pure
  raw-byte-pusher — no checksum selection, PID generation, or schedule
  tables. Deliberately breaks with any frame-aware assumption the
  deprecated linbr.hpp bridge's era might imply; that file is untouched
  (DEPRECATE, not ADAPT, per the Satellite Package Disposition table).
• include/rcp/can.hpp (ep_type 0x0B): Classical/FD/XL via an explicit
  FrameFormat sub-field, data frames only (no remote-frame shape at all),
  CAN XL payload bounded to a conservative single-AVTPDU ceiling
  (kMaxXlPayloadSingleAvtpdu, strictly below the spec's own 2054-byte
  kMaxXlPayloadSpec) consistent with milestone 52's already-decided
  fragmentation no-go, three independent per-phase bit-timing register sets
  (arbitration/FD-data/XL-data), CAN-XL-specific receive filters, and
  deliberately no TriggerRegistry — the one device-facing endpoint
  type in this codebase without a trigger-signal table, per the spec.
• include/rcp/iseled.hpp (ep_type 0x0C): native ISELED daisy-chain
  Instruction/Address/Data request and Address/Data/optional-native-CRC
  response shape. The optional native CRC is layered on top of, and has no
  dependency on, rcp/e2e.hpp's general RCP-level E2E CRC from v2.6.0 —
  additional, not a replacement.
• include/rcp/mdio.hpp (ep_type 0x0D): Clause-22/Clause-45-mode-selected
  register access. Built despite being omitted from the spec's own
  informative "ten interfaces" list, per the roadmap's explicit call.
• include/rcp/wakeup.hpp (ep_type 0x01): the fixed SleepCMD (0xA5)
  opcode — decoded independently of rcp/sequencer.hpp's
  RequestTypeOpcode taxonomy — wake-source pin monitoring, and the
  repeating WakeUp message handshake milestone 53 (v2.9.0) depends on
  directly.
• include/rcp/endpoint.hpp fills in the five previously-TBD ep_type id
  constants. DAC (0x0A) stays unallocated — explicitly out of scope per
  the roadmap (no functional-config chapter defined in v0.5.1_RC).
• New tests: tests/test_lin.cpp, test_can.cpp, test_iseled.cpp,
  test_mdio.cpp, test_wakeup.cpp, traced in .fusa-reqs.json under
  REQ-LINEP-*/REQ-CANEP-*/REQ-ISELED-*/REQ-MDIO-*/REQ-WAKEUP-*.
  The LINEP/CANEP prefixes (rather than LIN/CAN) are deliberate:
  those shorter ids are already used by the untouched, deprecated
  linbr.hpp/canbr.hpp bridge stubs' own requirements, and this
  milestone's native endpoint types needed non-colliding ids of their own.
• CMakeLists.txt/include/rcp/version.hpp bumped 2.6.0 → 2.7.0.
• ROADMAP.md gets a Done (v2.7.0): paragraph under milestone 51.

Test plan

• cmake -B build -DRELAY_BUILD_CLI=ON -G Ninja && cmake --build build --parallel — builds clean (pre-existing, unrelated rcp/sim.hpp build failure on this local toolchain reproduces identically on unmodified main; confirmed via git stash)
• ctest --test-dir build --output-on-failure — 57/58 pass (the 1 "failure" is rcp_sim not building, same pre-existing issue)
• New suites (rcp_lin, rcp_can, rcp_iseled, rcp_mdio, rcp_wakeup) all pass
• cpfusa check — 0 errors
• cpfusa lint — 0 errors (on a clean checkout matching CI's environment)
• cpfusa cyber — 0 errors
• cpfusa trace --req-coverage 100 — 464/464 requirements annotated and tested (100%)
• cpfusa verify — 57/57 ctest tests pass, .fusa-evidence.json generated
• relay conform --strict build/cpp-rcp — PASS (built from this repo's own RELAY sibling checkout)