Clear terminal input buffer before sending Aspire commands (#15863)

* Clear terminal input buffer before sending Aspire commands

Fixes #15587. When the user has pre-existing text in the Aspire terminal
input buffer, stop/restart/start commands get appended to it, making
the resulting command invalid.

Send a line-clearing control sequence (Ctrl+U on Unix, Escape on
Windows) before each command to discard any buffered input.

* Update extension/src/utils/AspireTerminalProvider.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Use platform-specific clear sequence: Escape on Windows, Ctrl+U on Unix

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: adamint

extension/src/utils/AspireTerminalProvider.ts

@@ -97,6 +97,15 @@ export class AspireTerminalProvider implements vscode.Disposable {
 
         const aspireTerminal = this.getAspireTerminal();
         extensionLogOutputChannel.info(`Sending command to Aspire terminal: ${command}`);
+
+        // Clear any pre-existing text in the terminal input buffer before sending the command.
+        // Unix (bash/zsh): Ctrl+U (\x15) clears the current line via unix-line-discard.
+        // Windows (PowerShell): Escape (\x1b) clears the current line in PSReadLine's default Windows edit mode.
+        // Sending \x1b alone (without a trailing bracket sequence) via a separate sendText call is safe —
+        // PSReadLine's escape-sequence timeout ensures it is processed as a standalone Escape keypress.
+        const clearSequence = process.platform === 'win32' ? '\x1b' : '\x15';
+        aspireTerminal.terminal.sendText(clearSequence, false);
+
         aspireTerminal.terminal.sendText(command);
         if (showTerminal) {
             aspireTerminal.terminal.show();