Merge pull request #715 from flyingrobots/task/714-persist-writer-epoch-fencing

Persist filesystem WAL writer epochs

Author: flyingrobots

.ban-nondeterminism-allowlist

@@ -11,10 +11,15 @@ std-fs crates/warp-core/src/causal_wal.rs native WAL filesystem adapter pending
 std-fs crates/warp-core/src/wsc/store.rs native WSC filesystem store adapter pending extraction to a boundary crate.
 std-fs crates/warp-core/src/wsc/view.rs native WSC file-open helper pending extraction to a boundary adapter.
 std-fs crates/warp-core/src/causal_wal_tests.rs WAL filesystem fixture I/O only.
+std-env crates/warp-core/tests/causal_wal_hardening_tests.rs WAL independent-process fixture environment handoff only.
 std-fs crates/warp-core/tests/causal_wal_hardening_tests.rs WAL filesystem fixture I/O only.
 std-env crates/warp-core/tests/external_action_protocol_tests.rs external-action filesystem WAL fixture temp directory selection only.
 std-fs crates/warp-core/tests/external_action_protocol_tests.rs external-action filesystem WAL fixture I/O only.
 std-process crates/warp-core/tests/external_action_protocol_tests.rs external-action filesystem WAL fixture temp directory disambiguation only.
+time-instant crates/warp-core/tests/support/child_process.rs bounded independent-process fixture deadline only.
+thread-sleep crates/warp-core/tests/support/child_process.rs bounded independent-process fixture polling only.
+std-fs crates/warp-core/tests/support/child_process.rs timed-out fixture cleanup only.
+std-process crates/warp-core/tests/support/child_process.rs bounded independent-process fixture execution only.
 std-env crates/warp-core/tests/bounded_workspace_observation_tests.rs bounded-observation filesystem fixture temp directory selection only.
 std-fs crates/warp-core/tests/bounded_workspace_observation_tests.rs bounded-observation filesystem fixture I/O only.
 std-process crates/warp-core/tests/bounded_workspace_observation_tests.rs bounded-observation filesystem fixture temp directory disambiguation only.

CHANGELOG.md

@@ -7,6 +7,17 @@
 
 ### Added
 
+- Strict filesystem WAL stores now persist a checksummed writer-epoch ledger
+  containing the active epoch, its exact latest closed predecessor, and final
+  LSN and commit-digest evidence. Bounded retention keeps ledger writes and
+  reopen validation independent of lifetime restart count. An OS-backed writer
+  lease—not the deterministic chain markers stored in the generic fencing,
+  process, host, and lease fields—refuses overlapping processes before append.
+  A recovered trusted host closes only an abandoned epoch under that lease and
+  derives a fresh, monotonically linked successor. Duplicate, stale, skipped,
+  regressed, or unfenced epoch chains fail closed. Independent-process
+  witnesses carry an external-action request, claim, settlement, and
+  effect-free replay across successive host processes.
 - Echo now consumes the exact independently verified Edict
   `workspace.patch.applyValidated@1` request through a capability-rooted
   single-file patch adapter. The request binds the prior bounded-observation