v0.1.0-alpha.5

Alpha pre-release v0.1.0-alpha.5

Built from main @ 84df99d.

Highlights since v0.1.0-alpha.4:
- Preemptive recovery for stale batches (danger detector, mempool flush, cascade invalidation)
- L1 view staleness checks and refined danger-zone detection
- Runtime worker lifecycle refactor (workers/error modules)
- Health endpoints (/livez, /readyz)
- EIP-712 domain hardening and structured startup config validation
- Expanded recovery and e2e test coverage

Artifacts (via Release workflow): linux amd64/arm64 sequencer binaries and canonical machine image tarballs.