refactor(workflow): S14 ProjectEngine merge queue deletion

[gsxdsm]

Stack Slice

• Slice: S14
• Milestone: Deletion
• Base branch: feature/workflow-owned-merge-s13-scheduler-policy-deletion
• Full plan: docs/plans/2026-06-09-003-refactor-workflow-owned-merge-full-migration-slices-plan.md

Goal

Remove production ProjectEngine merge queue policy and retain only explicit human/manual event entry points plus substrate helpers.

Dependency

S8 merge processing, S11 branch-group subgraphs, and S13 scheduler deletion.

Expected Scope

packages/engine/src/project-engine.ts; runtimes/in-process runtime; core store; merge lifecycle and deletion tests.

Expected Tests

No startup hidden enqueue, unpause wakes workflow work, manual merge event wakes merge node, stale mergeActive does not block workflow work, old queue APIs compatibility-only.

Exit Gate

No production caller starts merge processing outside workflow runtime.

Status

Draft stack placeholder. This PR reserves ordering and review context; implementation should replace or extend the handoff artifact before this slice is marked ready.

Implementation Added

• Added merge queue deletion guard test for workflow-work-processor.\n- The guard fails if workflow-owned merge processing depends on mergeQueue, enqueueMergeQueue, or ProjectEngine queue internals.

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[greptile-apps]

Greptile Summary

This draft stack-placeholder PR for S14 adds a plan doc and a static guard test asserting that workflow-work-processor.ts stays isolated from legacy ProjectEngine merge queue APIs (mergeQueue, enqueueMerge, ProjectEngine).

• s14-project-engine-merge-queue-deletion.md is a correctly formatted handoff artifact with accurate dependencies, scope, and exit gate — no issues.
• workflow-merge-policy-deletion.test.ts introduces a readFileSync-based guard that passes today; all seven assertions (four positive sanity checks + three negative isolation guards) are correct against the current processor source, but they share a single it block, which can obscure whether a future failure is a true regression or a broken sanity check.

Confidence Score: 5/5

Safe to merge as a draft placeholder; the guard test correctly verifies processor isolation today and the plan doc is accurate.

Both changed files are non-production additions. The guard test passes against the current processor source with no logic or data-path changes introduced. The plan doc is informational only.

No files require special attention beyond the single style note on the test's co-located assertion structure.

Important Files Changed

Filename	Overview
docs/plans/workflow-owned-merge-stack/s14-project-engine-merge-queue-deletion.md	New draft-stack-handoff plan doc for S14; accurately describes scope, dependencies, and exit gate — no issues.
packages/engine/src/tests/workflow-merge-policy-deletion.test.ts	New static guard asserting workflow-work-processor.ts is isolated from legacy merge queue APIs; all assertions pass, but positive and negative checks are co-located in a single it block which will produce ambiguous failures if the processor is refactored during S14.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["workflow-merge-policy-deletion.test.ts"] -->|"readFileSync"| B["workflow-work-processor.ts"]
    B -->|"positive: contains"| C["claimDueWorkflowWorkItem\nruntime.runWorkItem\n'merge' / 'manual-hold'"]
    B -->|"negative: not contains"| D["mergeQueue\nenqueueMerge\nProjectEngine"]
    E["project-engine.ts\n(59 legacy merge queue references)"] -.->|"not read by guard"| A
    style E stroke-dasharray: 5 5

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_{Reviews (9): Last reviewed commit: "test(FN-000): avoid freezing legacy merg..." | Re-trigger Greptile}

[gsxdsm]

expect(projectEngineSource).toContain("private mergeQueue") records the pre-deletion state.

Addressed: removed that legacy-state assertion. The guard now focuses on workflow processor isolation from mergeQueue, enqueueMerge, and ProjectEngine instead of freezing the queue field that the deletion slice is meant to remove.

[stage-review]

Ready to review this PR? Stage has broken it down into 2 individual chapters for you:

	Title
1	Document the ProjectEngine merge queue deletion plan
2	Enforce isolation from legacy merge queue

_{Chapters generated by Stage for commit 91366fd on Jun 16, 2026 9:19am UTC.}