网格渐变漂移

<!-- motion-registry-context:{"format":"1.0.0","recipe_id":"background.mesh-gradient-shift","recipe_version":"0.2.0","recipe_source":"recipes/background/mesh-gradient-shift/recipe.yaml"} -->
# Motion Registry Context

<!-- motion-registry-section:recipe-identity:start -->
## Recipe identity
- Recipe ID: background.mesh-gradient-shift
- Schema version: 0.2.0
- Recipe source: recipes/background/mesh-gradient-shift/recipe.yaml
<!-- motion-registry-section:recipe-identity:end -->

<!-- motion-registry-section:motion-intent:start -->
## Motion intent and scope
- Purpose (zh): 两个大面积柔光色场有限靠近并融合，为边缘标题保留清晰安全区。
- Purpose (en): Two large soft color fields converge and settle within a finite duration while preserving an edge-anchored title safe area.
- Scope: scene
- Complexity: intermediate
- Subjects: background
- Intents: decorate, reveal
- Use cases: social-video, presentation
- Recipe capabilities: gradient-lobes, finite-color-blend, title-safe-area
<!-- motion-registry-section:motion-intent:end -->

<!-- motion-registry-section:inputs:start -->
## Inputs
- title: string (required; default=IDEAS IN MOTION) — The title placed above the settling color fields.
- palette: enum (optional; default=amber-slate; options=amber-slate|ember-rose) — The controlled warm color-field palette.
<!-- motion-registry-section:inputs:end -->

<!-- motion-registry-section:normalized-timeline:start -->
## Normalized motion timeline (0 to 1)
- 0.08–0.28 · left-fade · opacity.fade → gradient-left · parameters={"from":0,"to":1}
- 0.14–0.38 · right-fade · opacity.fade → gradient-right · parameters={"from":0,"to":1}
- 0.18–0.68 · lobes-converge · transform.translate → gradient-left · parameters={"axis":"x","from":-0.1,"to":0,"unit":"relative-canvas"}
- 0.24–0.52 · title-reveal · opacity.fade → title · parameters={"from":0,"to":1}
- 0.44–0.70 · title-settle · transform.translate → title · parameters={"axis":"y","from":0.05,"to":0,"unit":"relative-canvas"}
- 0.74–1.00 · hold · state.hold → title · parameters={}
<!-- motion-registry-section:normalized-timeline:end -->

<!-- motion-registry-section:output-envelope:start -->
## Output envelope
- Aspect ratios: 16:9, 9:16, 1:1
- Duration: min 2.4s; preferred 3.2s; max 5s
<!-- motion-registry-section:output-envelope:end -->

<!-- motion-registry-section:acceptance:start -->
## Acceptance constraints
- finite-motion: The color fields settle into a stable hold with no looping motion.
- title-safe-area: The title remains readable and unobscured above both blurred color fields.
- distinct-background-grammar: The final frame contains no grid, particle, grain, node, line, or central metric card grammar.
<!-- motion-registry-section:acceptance:end -->

<!-- motion-registry-section:handoff-invariants:start -->
## Handoff invariants
- Preserve the subject, input meaning, event order, overlaps, final state, and approximate normalized timing.
- Keep the implementation deterministic and retain a readable, stable final hold.
- Treat the Recipe document as the source of truth; do not infer engine APIs in this shared core.
<!-- motion-registry-section:handoff-invariants:end -->