[GP1-S2] Filesystem Runtime WAL ACK Path

[flyingrobots]

Roadmap slice: GP1-S2
Goalpost: Goalpost 1: Durable Runtime WAL Join
Parent: #521
Related: #510, #518

Source: docs/design/wal-wsc-durability-roadmap.md on branch cycle/521-wal-wsc-storage-relationship at bde7957c.

Scope

Parent issues:
#510,
#518.

Scope:

• Add a host API for configuring a runtime WAL root backed by
  FilesystemWalStore.
• Commit accepted submissions and scheduler tick receipts through filesystem
  WAL before app-visible ACK/outcome success.
• Recover pending and decided submissions from the filesystem root after host
  reconstruction.

Acceptance:

• A test submits an intent through the filesystem runtime WAL ACK path,
  reconstructs a fresh host/recovery view from the WAL root, and observes the
  same submission id, envelope digest, receipt posture, and recovery
  certificate indexes.
• The app never receives the WAL root or store handle.

Witness:

cargo test -p warp-core --features "native_rule_bootstrap trusted_runtime host_test" --test trusted_runtime_host_loop_tests filesystem_runtime_wal_ack

Dedupe note

This is the PR-sized implementation slice for the roadmap item above. Existing umbrella or adjacent issues remain linked as Parent/Related rather than duplicated here.

[coderabbitai]

🔗 Related PRs

#247 - M2.1: DPO concurrency litmus (spec + tests) [merged]
#360 - feat(core): stage ticketed ingress and outcome observation [merged]
#368 - feat(core): connect installed contract intent pipeline [merged]
#379 - feat(core): commit runtime WAL ACK evidence [merged]
#550 - Expose braid membership history [merged]

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