fix: track all GUI goroutines with WaitGroup and ctx.Done() (Go Mistake #62)

Fire-and-forget goroutines in the tooltip setup, word-change handler, and
audio playback could write to freed Fyne widgets after the window was closed.
All four patterns are now fixed:

- setupTooltips() and the secondary-toolbar tooltip block: replaced
  time.AfterFunc(500ms) with wg-tracked goroutines using select/ctx.Done().
- handleWordChange(): replaced time.AfterFunc(100ms) with the same pattern.
- onWindowClosed(): added wordChangeTimer.Stop() to prevent its AfterFunc
  callback from firing after context cancellation.
- AudioPlayer: added ctx context.Context field + SetContext(); the
  post-playback goroutine now guards fyne.Do with ctx.Err() == nil, and the
  auto-play AfterFunc is replaced with a ctx-aware goroutine.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions