perf(react-icons): reuse canonical fonts instead of regenerating

[Hotell]

Summary

The react-icons build re-ran fantasticon 4× (~48s/variant) to generate font families that already exist in the repo-root fonts/ folder — the single source of truth, regenerated at release time by importer's deploy:fonts. This PR removes that redundant work: react-icons now just copies the canonical fonts.

Changes

1. Deterministic font generation — importer/generateFont.js

• formatOptions.ttf.ts = 0 pins svg2ttf's created/modified timestamps so font binaries are byte-deterministic across builds (WOFF/WOFF2 wrap the TTF bytes). This was the root cause of font binary churn between builds.
• Sort glob results so codepoint assignment is stable regardless of filesystem readdir order.

2. Stable cross-release codepoints — importer/package.json

• Seed Light & Resizable codepoints from the committed root fonts/ JSON. Previously they were unseeded and could drift on every build; now all four families are seeded.

3. react-icons copies instead of regenerating

• New scripts/copy-base-fonts.js copies the font binaries + glyph-named codepoint JSON from root fonts/ (skips the unused .css/.html fantasticon byproducts).
• generate:font is now that single copy step — the four generateFont.js (fantasticon) invocations are removed from the react-icons build.
• Removed the now-unused concurrently devDependency.

4. nx caching

• Added a cacheable deploy:fonts target (importer/project.json) keyed on assets/** + the generation scripts, output {workspaceRoot}/fonts.
• react-icons build cache inputs now include the root fonts/ artifacts, so it invalidates when fonts change.
• Renamed the nx project @fluentui/system-icons-processing → system-icons-processing (npm package name unchanged).

5. DRY cache inputs via composable named inputs

• Replaced duplicated/inlined input globs with composable namedInputs in nx.json, each defined once:
  • assets — assets/**
  • iconGenerationToolchain — shared importer/generate.js, replace-in-files.js, svgo.config.shared.cjs
  • fontGenerationToolchain — composes iconGenerationToolchain + generateFont.js, svgo.config.mjs, package.json
  • fontArtifacts — fonts/FluentSystemIcons-*.{ttf,woff,woff2,json}
• importer (deploy:fonts), svg-icons (build), and react-icons (build) now reference these instead of inlining the same globs.
• Fixed a dangling implicitDependency in svg-icons (@fluentui/system-icons-processing → system-icons-processing) surfaced by the rename.

Behavior note (Option A: pure copy)

Brand-new icons added between releases won't have font glyphs in react-icons until a release runs deploy:fonts (which precedes the react build in publish.yml). Published output stays correct.

Verification

• Full react-icons:build ✅ (no fantasticon runs)
• build-verify 127 tests ✅, convert-font.utils 8 tests ✅ — no snapshot changes needed
• react-icons lib/utils/fonts/* is now byte-identical to root fonts/ (expected one-time shift from raw → optimized geometry; functionally identical glyphs/codepoints)
• Two consecutive generateFont.js runs now produce byte-identical ttf/woff/woff2
• nx project graph resolves cleanly (no dangling refs); svg-icons:build produces a cache hit on re-run

Follow-up (not in this PR)

Regenerating the committed root fonts/ with the new deterministic bytes (deploy:fonts) is left as a separate, reviewable commit.

[github-actions]

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