feat(studio): the automation lane itself

Draws each automated parameter as its own lane under the audio clip, on the same
disclosure caret the keyframe lanes use — that caret is the DAW automation
triangle. One lane per parameter rather than a selector to swap between them, so
two envelopes can be read and edited without hiding either.

Double-click the line to add a point, drag to shape it, right-click a point to
remove it.

Three things here took more than one attempt, and the comments say why:

- **A dragged point did not move.** The live write deliberately skips the preview
  refresh — that is what keeps dragging from restarting playback — so the stored
  value does not move under the pointer. The lane keeps a local draft.
- **Releasing snapped it back.** The draft was dropped when the drag ended, which
  is before the persisted write comes around; it now lives until the automation
  it was drawn over actually changes.
- **A press was eaten.** Not stopping propagation let the timeline start its own
  gesture and swallow the second half of a double-click. The lane owns the press
  once it is live — and when it is not, it selects its clip instead, since lanes
  sit below the clip bar where the timeline's own selection handler never sees
  them.

The envelope is inset by the grab radius so a point at the clip's first or last
frame is drawn whole rather than half outside the lane, and clip time still lines
up with screen position because the inset and the offset cancel.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: vanceingalls