refactor(quickfiler): remove unused stackMovedItems parameter from MoveEmailsAsync (#629)

[drmoisan]

Suggested title

refactor(quickfiler): remove unused stackMovedItems parameter from MoveEmailsAsync (#629)

Summary

• Removes the unused stackMovedItems parameter from IQfcCollectionController.MoveEmailsAsync and
  its implementation — the undo stack was never populated from this argument.
• Updates the sole production call site (QfcFormController.EventHandlers.cs) to invoke the
  zero-argument overload.
• Updates four tests across two files whose call shape referenced the old signature: three mechanical
  fixes, one rewrite that preserves the early-return-branch coverage the old test happened to also pin.
• Rewrites the XML doc comment on the interface method as a <remarks> block explaining where the
  undo stack is actually populated, instead of leaving a stale <param> tag.
• No behavioral change: this is a same-process signature simplification with an unchanged call graph.

Why

Issue #469's investigation (defect 4) established that MoveEmailsAsync's stackMovedItems parameter
is never used to populate the undo stack — EmailFiler.PushToUndoStack writes onto the same global
SloStack instance directly (UtilitiesCS/EmailIntelligence/EmailParsingSorting/EmailFiler.cs:185-189).
Issue #468's branch could not remove the parameter itself because doing so required editing
QfcFormController.EventHandlers.cs, a file outside that branch's declared scope, so it added an
explicit discard (_ = stackMovedItems;) and deferred the actual removal to this issue (#629). Leaving
a discarded, unused parameter on a production interface is a maintenance hazard: a future reader may
reasonably — and incorrectly — assume it does something.

What Changed

Core feature (production code):

• QuickFiler/Interfaces/IQfcCollectionController.cs — Task MoveEmailsAsync(SloStack<IMovedMailInfo> stackMovedItems) → Task MoveEmailsAsync(); <param> doc replaced with a <remarks> block.
• QuickFiler/Controllers/QfcCollectionController.cs (line 2152) — parameter removed, _ = stackMovedItems; discard deleted, stale trace-log comment updated, doc comment rewritten.
• QuickFiler/Controllers/QfcFormController.EventHandlers.cs (line 228) — call site updated to await _groups.MoveEmailsAsync();.

Tests:

• QuickFiler.Test/Controllers/QfcCollectionControllerDefects468MoveTests.cs — 3 call sites updated mechanically; MoveEmailsAsync_WithNullStack_BehavesIdenticallyToAnEmptyStack rewritten to MoveEmailsAsync_WithEmptyItemGroupsToMove_DoesNotThrow, keeping the early-return-branch coverage it was the only test to exercise.
• QuickFiler.Test/Controllers/QfcFormControllerUndoHandoffTests.cs — one Moq Setup and one Verify updated to the zero-argument signature.

Docs/feature folder:

• spec.md, user-story.md, and a new atomic plan (plan.2026-09-02T11-00.md) authored for this feature folder, which previously held only issue.md.
• Baseline and final QA-gate evidence, a coverage-delta analysis, and this feature's policy-audit, code-review, and feature-audit artifacts.

Architecture / How It Fits Together

No architectural change. IQfcCollectionController remains a single-implementation, first-party
interface (QfcCollectionController) with a single production call site
(QfcFormController.EventHandlers.cs). The undo stack's actual population path
(EmailFiler.PushToUndoStack → Globals.AF.MovedMails) is unchanged and was never wired through this
parameter.

Verification

Completed:

• dotnet tool run csharpier check . — exit 0, no diffs.
• msbuild TaskMaster.sln /t:Rebuild /m /p:Configuration=Debug "/p:Platform=Any CPU" /p:EnableNETAnalyzers=true /p:EnforceCodeStyleInBuild=true — exit 0, 0 errors.
• msbuild TaskMaster.sln /t:Rebuild /m /p:Configuration=Debug "/p:Platform=Any CPU" /p:TreatWarningsAsErrors=true — exit 0, 0 errors.
• Full QuickFiler.Test suite via vstest.console.exe with coverage — 6949/6949 passing, both baseline and final.
• Coverage delta (using the reliable lines-covered/lines-valid sums, not the root Cobertura rate attributes, which are known-unreliable per open defects Bug: cobertura-package-rates-not-recomputed #529/Bug: cobertura-merged-class-methods-incomplete #530): line coverage +0.0078pp, branch coverage −0.0121pp (within run-to-run noise; no branching logic was touched by this change). Full analysis: evidence/qa-gates/p2-t6-coverage-delta.md.
• Diff footprint verified against origin/main: exactly the 5 production/test files predicted in spec.md, plus this feature folder's own docs/evidence. evidence/other/p1-t6-footprint-check.md.

Recommended:

• CI reproduction of the same toolchain pass and 6949/6949 test count.

Backward Compatibility / Migration Notes

Breaking change to IQfcCollectionController.MoveEmailsAsync's signature. This is not a published or
external API — it has exactly one production implementation and one production call site, both
first-party and updated in this same PR. No external consumer is affected.

Risks and Mitigations

• Risk: a missed mock/setup site elsewhere in the test suite would fail to compile.
  Mitigation: a full-repo grep for MoveEmailsAsync and Mock<IQfcCollectionController> was run
  before editing began and found all 6 call sites (4 direct + 2 mock), one more than issue.md
  originally anticipated (evidence/baseline/p0-t8-mock-sweep.md).
• Risk: deleting rather than rewriting the null-stack test could silently drop branch coverage on
  the early-return path.
  Mitigation: confirmed via grep this was the only test setting _itemGroupsToMove to an empty
  collection, and rewrote rather than deleted it.

Review Guide

Suggested order:

1. QuickFiler/Interfaces/IQfcCollectionController.cs — the signature change and doc-comment rewrite.
2. QuickFiler/Controllers/QfcCollectionController.cs — the implementation-side removal.
3. QuickFiler/Controllers/QfcFormController.EventHandlers.cs — the one-line call-site update.
4. QuickFiler.Test/Controllers/QfcCollectionControllerDefects468MoveTests.cs — 3 mechanical fixes plus the one rewritten test (see evidence/other/p1-t5-test-disposition.md for rationale).
5. QuickFiler.Test/Controllers/QfcFormControllerUndoHandoffTests.cs — the two Moq site updates.
6. The docs/features/active/2026-08-26-qfc-remove-stackmoveditems-parameter-629/ folder is documentation and evidence only; the two .cobertura.xml files are large and mechanical (raw coverage tool output), not hand-authored.

Follow-ups

None identified. This closes out the deferred cleanup that issue #468 explicitly left for a later issue.

GitHub Auto-close

• Closes Refactor: Remove the stackMovedItems parameter from MoveEmailsAsync #629