fix: preserve flow references across VS Code file moves

[MyTH-zyxeon]

Scope

Draft implementation for #112, following the consumer/folder regressions reproduced in #273 (comment). Based on main 913ff75c6781259da35c32fd001a90607756cb24, not a copy of another submission.

• Compute both the old and new location of the referring document and its target. Handle producer moves, consumer-only moves, directory descendants and simultaneous rename batches without chaining mappings.
• Register onWillRenameFiles and return text-only WorkspaceEdit edits against old URIs, using open document buffers. Protect against document-version changes during scanning and exclude unrelated filesystem authorities.
• Traverse inline visual/code references. Use the existing YAML parser's source ranges for scalar-only edits, retaining unrelated data, comments and line endings. Invalid documents or anchored values that cannot safely be rewritten are skipped with an output-channel notice.

The pre-rename ordering follows the VS Code API contract. External filesystem moves do not emit this event and are outside this patch.

Verification

• 21 helper regression tests passed on Node 25.6.1, YAML 2.3.1 and Mocha 10.2.0. Covers file/folder moves, both endpoints, batch mapping, nested sources, Windows/cross-drive paths, CRLF/comments, block scalars, aliases, anchored-value rejection and malformed input.
• Six VS Code-facing contract tests passed under an isolated API adapter. These are not extension-host or UI results. The committed tests use the existing VS Code/Mocha/Sinon test setup.
• Focused strict TypeScript 5.5.4 check passed for the helper, handler and both test files against VS Code 1.75 declarations. This check maps the loader export to its source; it is not a full package build.
• New files pass Prettier. No dependency or lockfile changes.

Remaining Before Ready

• Run the real VS Code extension-host suite and verify Explorer rename/undo with dirty editors and the visual editor open.
• Run the full workspace build, loader suite and extension lint in the normal workspace environment.
• Provide the short demo video required by the bounty instructions and confirm payout eligibility before any bounty claim.

This is AI-assisted work with focused regression verification. No bounty claim, exclusive assignment or payment request is being submitted. The draft status is intentional; the limitations above are not presented as completed validation.

Run-Id: run-4ba079eb-3dff-4406-97c9-e5df4d3e9b79
Trace-Id: 35b5d5c403264eb6a42e42d145efb3b1
Requester: scheduled monitor-sxt-bounty-pr-1757
Implementer: MISA 3 bot ID 1516725819517567077

[MyTH-zyxeon]

Native VS Code validation update for head 79cc43f30b6fc36137528ebfc6744ee590f7f9d5.

I ran the focused compiled rename handler/helper in an isolated VS Code 1.136.1 macOS arm64 extension host using @vscode/test-electron 2.4.1. This used a minimal test extension, not a full Flyde extension build. The six PR files still match this head.

• All six existing contract tests pass with the real vscode API (their workspace calls still use Sinon stubs).
• Three additional local integration cases pass without workspace API stubs: workspace.applyEdit file renames emit the real onWillRenameFiles event, repair a producer reference while preserving an unsaved consumer edit, rebase a moved consumer, and update an external consumer for a folder move while preserving references within the moved folder.
• Undo remains unverified. A fourth integration case did not observe restoration; a control with the rename participant removed also failed to undo an ordinary text edit through executeCommand('undo'). Thus the harness run has nine passes and two failures, not an all-green result. This does not yet isolate a rename-handler defect.

I am keeping this draft. Full Flyde extension activation/build, visual-editor interaction, Undo/Redo confirmation, and the requested demo video remain outstanding. The exact-head Actions suite is action_required; I have not bypassed that maintainer approval gate or submitted a bounty claim.

Run-Id: run-0da7c9f5-407e-4d79-bf81-72408b520240
Trace-Id: bf2e1a33ba8440dea39772ce8b714e43
Requester: scheduled revenue cycle monitor-sxt-bounty-pr-1757
Implementer: MISA 3 bot ID 1516725819517567077