Add reconciliation file write-through

workplans/STATE-WP-0048-ui-state-change-reconciliation.md

@@ -72,7 +72,7 @@ pin the write-through, deferred, and human-confirmation decisions.
 
 ```task
 id: STATE-WP-0048-T02
-status: in_progress
+status: done
 priority: high
 state_hub_task_id: "50c20ddf-f039-418b-a763-7a8f581be5b0"
 ```
@@ -90,11 +90,15 @@ current/target status, file-backed flags, reconciliation class, reason,
 follow-up action, and `write_through_result: not_attempted`. Dashboard wiring
 and write-through execution remain for the next slice.
 
+Result 2026-05-23: the API contract now also supports `apply: true` for safe
+write-through changes. Unsafe classifications return `not_applicable` instead
+of mutating files or DB state.
+
 ## T03 - Implement File Write-Through For Safe Changes
 
 ```task
 id: STATE-WP-0048-T03
-status: todo
+status: done
 priority: high
 state_hub_task_id: "c0a4e976-81fb-4fe3-a8a9-b8262e2c1c85"
 ```
@@ -106,6 +110,11 @@ the repo file, then sync the DB. Preserve formatting and existing
 Done when common dashboard transitions such as `active -> backlog` or task
 status updates can update the file representation deterministically.
 
+Result 2026-05-23: added workplan-file helpers and write-through support for
+file-backed workstream status and linked task status changes. The endpoint
+patches the workplan file first, then updates the DB status, and returns the
+relative workplan path plus `write_through_result: applied`.
+
 ## T04 - Queue Reconciliation For Deferred Changes
 
 ```task