fix: emit line event when command output starts

This fixes an issue where commands that wait for input (like 'cat'
without arguments) would hang indefinitely because no 'line' event was
emitted. The terminal would receive the VSCode shell integration marker
indicating command output has started, but since there was no actual
output yet, the UI would not proceed.

By emitting an empty line event when command output starts, we ensure
the UI can proceed even when a command is waiting for input, preventing
the task from hanging.

Thank you @cte for pointing this out in the PR development process.

Signed-off-by: Eric Wheeler <roo-code@z.ewheeler.org>

src/integrations/terminal/TerminalProcess.ts

@@ -206,6 +206,7 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 						commandOutputStarted = true
 						data = match
 						this.fullOutput = "" // Reset fullOutput when command actually starts
+						this.emit("line", "") // Trigger UI to proceed
 					} else {
 						continue
 					}