feat(tui-components): add animated backgrounds and motion storybook

[CSRessel]

Adds a reusable Ratatui MotionBackground widget for onboarding and other full-screen experiences. Applications render it first, then place existing forms or menus over its optional quiet area. The caller owns the terminal, input, redraw cadence, animation time, and transition progress; MotionState provides an optional transition controller. The widget also supports palettes, ASCII, reduced motion, and clipped viewports.

The motion_storybook example loops between dots and braille formations, with platoon and muster variants and no UI overlays. --at-ms N pauses at an exact story time for reproducible review. Snapshot coverage includes 16 buffer fixtures and 10 paired text/ANSI terminal captures covering endpoints, inward and outward zoom, and narrow viewports. Fixed times include ambient motion as well as zoom progress.

Frame-local geometry caches, prepared style ramps, skipped hidden fields, and buffered terminal writes reduce measured headless p95 frame work by 21–26% while preserving 1,160 sampled glyph/style fingerprints. Ratatui continues to perform incremental terminal diffs. Large live PTY viewports still miss some 25 FPS deadlines; these measurements do not establish graphical terminal presentation FPS. Reproduction scripts, raw data, and limitations are in the performance report.

Validation:

• Built all component examples with Rust 1.90.
• cargo test -p nori-tui-components -- --include-ignored --test-threads=1: 127 tests passed, including the isolated tmux storybook tests and doctest; snapshot updates disabled for the verification run.
• Reviewed and accepted the new snapshots; all 10 terminal text grids match their corresponding deterministic buffer fixtures, with RGB styling retained in ANSI captures.
• just fix -p nori-tui-components and just fmt passed.
• Final rebuilt example smoke check verified the exact paused muster return frame, s seeking to the inward frame, clean exit, and terminal mode restoration.

Try from nori-rs/:

cargo run --release -p nori-tui-components --example motion_storybook
cargo run --release -p nori-tui-components --example motion_storybook -- --muster
cargo run --release -p nori-tui-components --example motion_storybook -- --muster --at-ms 3600