Phase 4.1: Cross-platform font spike

[danielmrdev]

Parent

Part of #25 — Phase 4: Settings and appearance.

What to build

Establish the two font capabilities every other font-dependent Phase 4 slice relies on, and verify them on each supported platform before product code claims them: resolving the operating system's configured monospaced Typeface rather than an accidental renderer generic, and safely registering app-local TTF bytes and reflowing the editor when a Typeface or weight changes.

Acceptance criteria

• A cross-platform adapter resolves the OS-configured monospaced Typeface on Linux, macOS, and Windows, distinct from the renderer's generic monospace fallback.
• Bundled and cached TTF bytes register into Lettera's process-local font database and render in the editor.
• Changing Typeface, real weight, or size live reflows editor layout safely without corrupting Document content, undo/redo history, or logical caret offset.
• A selected Typeface's real weights match reliably; no synthetic bold and no unverified variable-font axis behaviour is assumed.
• Evidence, verified behavior, and remaining limits are recorded in the font-delivery research note; the production plan does not claim behavior the spike did not verify.

Blocked by

None — can start immediately.

[danielmrdev]

Cross-platform status:\n\n- Automated CI (build/clippy/tests) running on macOS and Windows runners via PR #34.\n- OS-dependent spike tests are Linux-gated; the remap test runs on all platforms.\n- Manual macOS/Windows verification (OS monospace resolution, visual relayout, cache/offline recovery, live system-theme reaction) deferred to Phase 4.7; owner has physical machines for both.

[danielmrdev]

Closed after merge of #34. Spike verified on Linux (OS monospace resolution via fontconfig, app-local TTF registration, real-weight matching, family-driven reflow). Automated CI green on Linux/macOS/Windows. Manual macOS/Windows verification deferred to Phase 4.7 (physical machines) and tracked in docs/font-delivery-research.md.