feat(FN-000): claim workflow work in scheduler substrate

Fusion-Task-Id: FN-000

docs/plans/workflow-owned-merge-stack/s03-generic-scheduler-claim.md

@@ -0,0 +1,46 @@
+---
+title: "S03: generic scheduler claim path"
+type: refactor
+status: draft-stack-handoff
+date: 2026-06-09
+slice: S03
+milestone: "Foundation"
+origin: docs/plans/2026-06-09-003-refactor-workflow-owned-merge-full-migration-slices-plan.md
+stack_base: feature/workflow-owned-merge-s02-merge-request-projection
+---
+
+# S03: generic scheduler claim path
+
+## Stack Role
+
+This draft PR reserves the S03 review slot in the workflow-owned merge,
+retry, scheduling, and recovery migration stack. It is intentionally a handoff
+artifact, not the completed implementation for this slice.
+
+## Milestone
+
+Foundation
+
+## Depends On
+
+S1 workflow work-item schema and store API.
+
+## Goal
+
+Teach Scheduler to claim due workflow work items while preserving existing task dispatch behavior.
+
+## Expected File Scope
+
+packages/engine/src/scheduler.ts; packages/engine/src/workflow-task-runtime.ts; packages/engine/src/project-engine.ts; scheduler/workflow dispatch tests.
+
+## Expected Tests
+
+Due-work claiming, retryAfter delay, capacity holds, user pause exclusion, stale lease reclaim, and remote dispatch.
+
+## Exit Gate
+
+A workflow work item can be dispatched end to end in tests without constructing a merge queue branch.
+
+## Full Plan
+
+See `docs/plans/2026-06-09-003-refactor-workflow-owned-merge-full-migration-slices-plan.md`.