feat: inline conversion with status updates, cwebp support, v0.1.4

- Conversion now happens inline on the file list — status column updates
  from idle → converting... → done/error in place (no separate screen)
- Fixed value-receiver bug in convertNext() that prevented 'converting'
  status from being displayed
- Added cwebp fallback for PNG/JPEG → WebP (ffmpeg webp encoder often
  missing on macOS)
- Format selector arrows hidden during conversion/results states
- Simplified to 2 states: stateFileList + stateResults
- Added tests for conversion state machine and view rendering

cli/internal/update/update.go

@@ -14,7 +14,7 @@ import (
 
 const (
 	// CurrentVersion is the embedded build version. Updated at release time.
-	CurrentVersion = "0.1.3"
+	CurrentVersion = "0.1.4"
 
 	repoOwner = "noauf"
 	repoName  = "Transmute"