feat: add loader component with seventeen variants

[starc007]

What

New `loader` component (motion category) — one `Loader` with 17 variants off a single `variant` prop:

• spinner — ring + rotating arc
• dots — bouncing dots
• bars — equalizer bars
• dot-matrix — 3×3 LED grid, diagonal wave
• dither — 4×4 grid dissolving in Bayer-matrix order
• morph — SVG path morphing circle → square → triangle → hexagon → diamond, each shape holds before flowing to the next
• comet — head + fading trail orbiting
• scramble — "LOADING" glyph-scrambling then resolving
• metaballs — two blobs merging via SVG gooey filter
• newton — Newton's cradle
• helix — DNA double helix of dots
• percent — 0→100 counter + fill bar
• ascii / ascii-line / ascii-braille / ascii-blocks / ascii-bounce — terminal-style frame spinners

Details

• One `size` prop scales everything; `speed` controls cycle time; `currentColor` so it inherits text color.
• `role="status"` + `aria-label` + sr-only label.
• Reduced motion swaps every transform for a calm opacity pulse.
• Morph uses SVG `d` interpolation (clip-path polygons don't tween reliably in framer) with doubled keyframes so each shape fully forms and holds.

Test plan

• `bun run check` clean (typecheck, lint, registry — 42 components)