docs: v0.138.0 -- citation backfill batch 18: WAKEUP (issue #164)

[SoundMatt]

Summary

Phase 2 (issue #164) citation-backfill batch 18: WAKEUP (Wakeup control endpoint).

Cited 13 of 16 remaining uncited REQ-WAKEUP-* requirements against TC18 §13.7.2, several cross-referencing the module's own pre-existing tc18-gap entries (REQ-WAKEUP-017-022) rather than implying full conformance where the implementation is a documented, reduced model:

• REQ-WAKEUP-002 — lifecycle-gated functional-config writability (§12.3.1.2/.3, reused basis)
• REQ-WAKEUP-003-004 — wake-source assertion, against Table 36/37, cross-referencing 021/022's reduced single-sense/single-latch modeling
• REQ-WAKEUP-005-008 — wup_status latch primitives, against Table 36, cross-referencing 021
• REQ-WAKEUP-010-013 — SleepCMD request/response, against Figure 22 + the 0xA5 opcode + sleep-handshake prose, response pair cross-referencing 019's divergence (positive-form refusal, not an error response)
• REQ-WAKEUP-014-015 — WakeUp message pair, against the repetitive-message prose, cross-referencing 017's divergence (no wake-up source field carried)

Left uncited: REQ-WAKEUP-001 (zero-init), REQ-WAKEUP-009 (strerror()), REQ-WAKEUP-016 (echo-detection helper — implementation convenience, no direct TC18 text).

Also records a scoping finding: MDIO (16 uncited) was investigated as the next candidate first and rejected — its own file header self-documents essentially the entire wire layout as non-TC18 original design (already tracked as tc18-gap #21/#22 there too), leaving only ~1 genuinely citable requirement. Not a good batch; can be revisited as a 1-item cleanup later.

Verification

• Purely additive .fusa-reqs.json change; no source/test code touched.
• Full build: 69/69 targets. Full test suite: 64/64 passed.
• cfusa check: 0 errors.
• cfusa trace --req-coverage 100 --sec-tested 100: 100%/100%.
• .fusa-reqs.json JSON-validated.
• Citation count: 570/1028 (55.4%) → 583/1028 (56.7%). WAKEUP module: 6/22 → 19/22.

Ref: issue #164.