Stream Glyphs imports in bounded batches

[kostyafarber]

Summary

• route .glyphs and .glyphspackage through the existing FontImport pipeline
• parse each Glyphs source once, publish its header/directory, and convert Shift glyph geometry in bounded Rayon batches
• preassign glyph identities so components resolve independently of batch order
• publish directory-only workspaces and acquire component closures lazily from SQLite

Verification

• cargo test -p shift-backends
• cargo test -p shift-workspace
• cargo clippy -p shift-backends -p shift-workspace --all-targets -- -D warnings
• full pre-commit suite

Profiling

The release profile_streaming_import control imports the repository's 327-glyph Homenaje fixture in 22.4 ms end-to-end. The reported large Glyphs corpus still needs to be rerun on the originating Mac; the upstream glyphs-reader parse remains eager, while Shift conversion, packing, compression, and SQLite publication are now bounded.