fix(#112): rewrite file import paths on Explorer rename (+ recovery)

[projectcarbonfiber]

Fixes #112
/claim #112

Summary

When a .flyde (or code) file that is imported via source: { type: file } is moved in the VS Code Explorer, the importer’s stored relative path went stale and resolution failed (join(flowDir, stored)).

This PR keeps imports working with a dual path:

1. Primary (Explorer renames): onWillRenameFiles + WorkspaceEdit rewrites only the data scalars of source: { type: file } entries (including nested inline visuals). Pure path math lives in @flyde/loader (getReferenceEditsForRename) so the VS Code adapter stays thin. Edits apply at the old URI before the rename, which plays well with dirty buffers / undo.
2. Fallback (external / already-stale paths): if the stored path no longer exists at resolve time, recoverMovedFileSource searches the project for the same basename (skipping node_modules / .git / build dirs) and prefers the best path-suffix match.

Package and custom sources are left untouched. Absolute refs, Windows paths, batch/folder renames, and most-specific overlapping maps are covered by hermetic tests.

Acceptance criteria

• Moving an imported producer (.flyde / .flyde.ts) updates importers’ relative paths
• Moving a consumer rebases its remaining relative imports
• Folder / batch renames and most-specific overlapping maps work
• Nested inline visual source.file entries update
• Package / custom sources unchanged
• Dirty-buffer-friendly (onWillRenameFiles + open document text)
• Stale paths after an out-of-IDE move can still resolve via recovery

Test plan / results

Loader (hermetic), run from loader/:

npx mocha 'src/serdes/rename-references.spec.ts' \
  'src/resolver/server/recoverMovedFileSource.spec.ts' \
  --require ts-node/register --no-timeout

Result: 26 passing (21 rename-reference cases + 5 recovery cases), covering producer/consumer/folder/batch/prefix-safety/simultaneous/most-specific/package-skip/inline/CRLF/aliases/absolute/Windows/cross-drive/invalid YAML/block scalars/anchors + recovery happy/moved/collision/null/node_modules skip.

VS Code contract suite added at vscode/src/test/suite/renameReferences.test.ts (unsaved docs, consumer rebase, malformed skip, authority filter, mid-scan version bump, waitUntil registration). Full extension host run not executed in this environment (pre-existing @flyde/editor build deps); logic under test is the same pure helper covered above.

Notes

Several open PRs already explore Explorer rewrite; this submission focuses on a clean loader-owned rewrite API plus an explicit recovery fallback for moves that never went through VS Code. Happy to adjust scope if maintainers prefer rewrite-only.