0.2.0

More natural motion and a tighter battery/performance contract.

Note: the drop-in KWave overload gained two parameters, which changes its binary signature.
Source-compatible (the new parameters are trailing with defaults), but consumers compiled against
0.1.0 must recompile — standard for a 0.x minor.

Added

• Crest sway: each breathing layer's crests now lean slowly side to side on top of the
  amplitude breathing, so the surface rolls organically instead of only pulsing vertically. The
  sway is scaled by the layer's breathDepth (a breathDepth = 0 layer has zero sway and stays
  fully static), runs slower than the breathing, and is phase-decorrelated from it per layer.
• Elevation-style depth shading. Each wave now casts a diffuse, blur-like shadow on the
  content behind it (background and further-back layers), like stacked translucent sheets,
  and its crest is gently lit from inside the fill (the top of each wave's gradient is lifted
  toward WaveColors.highlight) instead of carrying a separate highlight shape — a thin band
  tracing a wide crest read as a "string". The render pass is interleaved per layer
  (shadow → fill, back to front), so a shadow can never bleed over a nearer wave — the 0.1.x
  two-pass design let back-layer shadows smear across the front waves, and its straight vertical
  fades washed the waves instead of shading their edges. ShadowMode keeps its semantics for the
  shadow (Auto by luminance, Custom.alpha = the shadow's total peak opacity, None disables
  it), and every layer now gets the FX, including the front-most.
• Per-wave depth gradient fill. Each layer's body is now painted with a subtle vertical
  gradient (its palette color at the crest, slightly darkened toward the bottom) instead of a flat
  color, giving every wave internal depth.
• WaveColors.withBackground(...): decouples the backdrop from the wave palette. The factories
  still build a coherent scene from one set of colors; withBackground(color) /
  withBackground(top, bottom) / withBackground(stops) then replace only the background,
  leaving the wave fills and highlight untouched. withBackground(Color.Transparent) is the
  waves-only mode: the renderer skips the background pass entirely, so KWave can sit on top of
  caller-provided content (locked by the new kwave_waves_only golden).
• sway parameter on WaveConfig and WaveConfig.generate: the config-wide weight of the
  crest sway, coerced >= 0. 1 (default) is the nominal organic roll; 0f disables the sway and
  restores the exact 0.1.x waveform (breathing without sway).
• drift parameter on the drop-in KWave: a gentle ambient horizontal travel in radians of
  phase per second, parallaxed per layer by WaveLayerSpec.speed. Default 0.05 (a full phase
  cycle ≈ 2 minutes); 0f removes the travel. Combine drift = 0f with WaveConfig.sway = 0f to
  fully restore the in-place motion of 0.1.x.
• maxFps parameter on the drop-in KWave: an optional cap on the animation update rate.
  Skipped frames publish no state, so nothing is invalidated, re-drawn, or composited — a large
  battery win on 120 Hz displays (24–30 is usually indistinguishable for this slow motion).
  <= 0 (the default) updates on every display frame.

Changed

• Default drop-in motion is now breathing + crest sway + slow drift (was: strictly in-place
  breathing). Both new strands are subtle and sinusoidal, and each has an off switch (drift = 0f,
  WaveConfig.sway = 0f).
• The stateless KWave(config, phase, time) overload paints different pixels than 0.1.0 for
  layers with breathDepth > 0 (the sway term participates in the waveform; it stays a pure
  deterministic function of its inputs). Downstream screenshot goldens must be re-recorded, or pass
  a WaveConfig with sway = 0f for the 0.1.x waveform.
• speed and drift are integrated per frame instead of being multiplied by the total
  elapsed time, so changing either live (a slider, an animated transition) alters the tempo from
  that frame on without snapping the accumulated position. Note that speed does not scale
  drift; use isPlaying = false to freeze all motion.
• Frame-driven state is read in the draw phase. A running animation now invalidates only the
  draw pass; the KWave composable no longer recomposes on every frame.
• The renderer caches all frame-invariant paint objects. The background gradient, per-layer
  resolved fill colors, and per-layer shadow/highlight band brushes are rebuilt only when the
  config or the canvas height changes; a steady frame allocates zero Paths and zero Brushes
  (previously the brushes were re-created every frame). The Path cache survives any config change
  that keeps the layer count.
• The waveform engine computes in double precision and the drop-in integrates elapsed time in
  double precision, so the motion keeps frame-level smoothness after days of continuous runtime
  (kiosk / always-on screens). A Float seconds accumulator degraded after a few hours.
• WaveColors now implements structural equality (equals/hashCode/toString). Two factory
  calls with identical inputs compare equal, so a WaveConfig rebuilt with the same values keeps
  matching remember keys (including the renderer's internal cache) instead of being treated as a
  new configuration.

Fixed

• isPlaying = false no longer pumps frames. The frozen loop previously kept a
  withFrameNanos pending on every frame (only to track the clock baseline), forcing the frame
  clock to keep producing frames at the display rate while visually frozen. The loop now truly
  suspends (zero frames, zero rendering work) and resumes without a time jump.
• Changing speed mid-animation no longer snaps the wave. It was previously multiplied by the
  total elapsed time, so a live change rescaled all accumulated history (the jump grew with
  uptime); it is now integrated per frame (see Changed).

Full Changelog: 0.1.0...0.2.0