fix(studio): surface fromTo from-state in GSAP design panel (#1122)

* fix(studio): surface fromTo from-state in GSAP design panel

Closes #1121.

The core already parsed, serialized, and mutated fromProperties end to end
(gsapParser.ts, applyUpdatesToCall, buildTweenStatementCode). The panel
never wired it in — AnimationCard only read animation.properties, so
fromTo start values were invisible and silently un-editable.

Changes:
- files.ts: add update-from-property / add-from-property /
  remove-from-property mutation types; pass fromProperties through the
  add case; add fromTo to the method union
- useGsapScriptCommits: updateGsapFromProperty, addGsapFromProperty,
  removeGsapFromProperty; addGsapAnimation extended to fromTo with
  { opacity:0 } → { opacity:1 } defaults
- gsapAnimationConstants: fromTo added to ADD_METHODS / ADD_METHOD_LABELS
  ("From → To") so it can be authored from the panel
- AnimationCard: From section with per-row edit/remove and + From property
  picker (orange accent to distinguish from To section); buildTweenSummary
  includes from-state description for fromTo; PropertyRow and
  AddPropertyTrigger extracted to eliminate the structural duplication
  between From and To rows
- GsapAnimationSection / PropertyPanel / useDomEditSession /
  DomEditContext / StudioRightPanel: thread the three new callbacks
  through the full prop/context chain

* test(studio): add API-level tests for fromProperties mutation routes

Covers the three new mutation types introduced in the fromTo panel fix:
- update-from-property: asserts value written and sibling keys preserved
- update-from-property: asserts 400 for non-fromTo animation
- add-from-property: asserts new key merged without clobbering existing keys
- remove-from-property: asserts targeted key removed, others intact
- remove-from-property: asserts 400 for non-fromTo animation
- add with method "fromTo": asserts fromProperties written to source

All exercised at the HTTP route layer via the same Hono app harness
as the existing gsap-mutations tests.