[CA-01-S2] Persist and recover causal-anchor admissions through the WAL

[flyingrobots]

Goal

Give causal-anchor admission a canonical WAL transaction and recovery path.

Acceptance criteria

• The WAL has explicit causal-anchor admission transaction and record kinds with stable numeric codes.
• One committed transaction atomically records the canonical anchor and its Echo admission receipt.
• Payload codecs reject truncation, trailing bytes, malformed enum values, and duplicate required frames.
• Recovery returns only fully committed, internally consistent admissions.
• A failed WAL commit yields no admitted anchor result.
• Deterministic restart and corruption witnesses cover the new record.

[coderabbitai]

🔗 Related PRs

#358 - feat(core): add admission evidence boundaries [merged]
#379 - feat(core): commit runtime WAL ACK evidence [merged]
#598 - feat(warp-core): add filesystem WAL failure atomicity [merged]
#609 - feat(warp-core): project WAL recovery evidence [merged]
#618 - Lock retained evidence crosswalk [merged]

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[flyingrobots]

Implemented in 5e63da9 and hardened in 75ac3b2. Causal-anchor admission has stable WAL transaction/record kinds, atomic fact+receipt commit, strict codecs, committed-only recovery, sealed reconstruction evidence, and restart/corruption/failure witnesses.