UX foundation W1 — bundle fonts + widgets.rs + slop kill

[hellno]

Wave 1 of the UX foundation overhaul (DESIGN.md v2, commit a92fb0f).

Goal: make the foundation real and consistent.

• Bundle General Sans + JetBrains Mono into crates/deckard-app/assets/fonts/; uncomment add_fonts in main.rs (C1: the app currently renders in the OS system font).
• Build crates/deckard-app/src/widgets.rs (the DESIGN.md §Enforcement vocabulary): caution_line, section_label, short_addr, identity_mark (monogram, never blank), and consolidate the 3-4 divergent copies of each.
• Humanize provider/read errors (no raw RPC string in the status strip); parameterize humanize_deny(reason, noun) so send says "transfer".
• Slop kill: delete the on-canvas keyboard-hint chip row; ⚠ emoji → caution_line; orphan — → skeleton/empty; em-dash sweep in UI copy; "Welcome to Deckard" → the promise; dead display_name + tray-feature leak; "broadcast" → "sent".

DoD: cargo fmt --all --check, just check, cargo test --workspace, no new deps, native before/after screenshots. Edit-only subagents + foreground builds (gpui watchdog).