fix(assets): remove '* Temp (LTR|RTL)' staging folders to restore build determinism

[Hotell]

Follow-up to #1086 — must merge after that PR.

Removes the 20 assets/* Temp (LTR|RTL)/ folders flagged as known-dirty by the detector introduced in #1086, and drops the matching KNOWN_DUPLICATE_SOURCE allowlist from importer/generate.js. With the allowlist gone, the default --on-duplicate=fail now guards against any new colliding asset folder being added.

Why

These folders contain SVGs named after the opposite icon (e.g. assets/Arrow Undo Temp RTL/SVG/ic_fluent_arrow_redo_*.svg), have no metadata.json, and write into the same flat intermediate/ filenames as the canonical asset folders. The async copy in generate.js then resolves the collision non-deterministically, producing different lib/atoms/svg/*.js, barrel chunks, and font binaries on each clean build. #1086 added a detector + temporary allowlist for them; this PR removes the underlying source data and the allowlist.

Folders removed (20, 272 files total)

Icon family	Folders
Arrow Redo	assets/Arrow Redo Temp LTR/, assets/Arrow Redo Temp RTL/
Arrow Undo	assets/Arrow Undo Temp LTR/, assets/Arrow Undo Temp RTL/
Table Freeze Column	assets/Table Freeze Column Temp LTR/, assets/Table Freeze Column Temp RTL/
Table Freeze Column And Row	assets/Table Freeze Column And Row Temp LTR/, assets/Table Freeze Column And Row Temp RTL/
Text Align Left	assets/Text Align Left Temp LTR/, assets/Text Align Left Temp RTL/
Text First Line	assets/Text First Line Temp LTR/, assets/Text First Line Temp RTL/
Text Grammar Arrow Left	assets/Text Grammar Arrow Left Temp LTR/, assets/Text Grammar Arrow Left Temp RTL/
Text Grammar Arrow Right	assets/Text Grammar Arrow Right Temp LTR/, assets/Text Grammar Arrow Right Temp RTL/
Text Hanging	assets/Text Hanging Temp LTR/, assets/Text Hanging Temp RTL/
Text Paragraph	assets/Text Paragraph Temp LTR/, assets/Text Paragraph Temp RTL/

Each folder contained only PDF/ and SVG/ subdirectories with .pdf / .svg files — no metadata.json or other tracked files.

Verification

Test	Result
node importer/generate.js … --target=react --on-duplicate=fail on full assets/	0 collisions, exit 0
Synthetic two-folder collision fixture	exit 1 (detector still works)
Two clean nx run react-icons:build runs → diff -rq lib/ lib-cjs/ metadata.json	No differences — React icon output is now byte-deterministic

Out of scope

• The detector itself (already on main via feat(importer): detect duplicate destination filenames in generate.js #1086)
• Any other asset directories — only the 20 explicit Temp (LTR|RTL) ones

Reviewer checklist

• Design / icon-asset team: confirm these folders were staging artifacts and are not referenced by any active pipeline (iOS, Android, Flutter, docs generators)
• Confirm monosize.baseline.json doesn't need updating (no React icon export changes expected — canonical folders already provide the same names)

Stack note

This PR's diff against main currently includes the commit from #1086 (a4427400a2). Once #1086 merges, this PR will rebase automatically and show only the cleanup commit.

[github-actions]

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[etudie]

Thank you for the bump, missed this PR!
Noting your rebase comment.

Looks good!