Make sure command finished event is fired when chat agent runs a command

[meganrogge]

When the Basic shell integration strategy is chosen due to either a screen reader being present when using pwsh (which lacks PSReadline support) or some other clashing configuration, partialCommandDetectionCapability vs CommandDetectionCapability is used.

RunInTerminalTool relies on onDidEndTerminalShellExecution firing in order to consider the terminal command running step completed. If that does not occur, the tool will continue to hang and wait for a done event that never comes.

onDidEndTerminalShellExecution waits for onCommandFinished to be fired from its capability. In the case of the partialCommandDetectionCapability, that happens only onEnter IE when enter is sent to the terminal. That does not occur when the chat agent sends the command, so no onCommandFinished gets fired and thus chat hangs and never believes the command has completed even though it has.

The fix is to also listen to onWriteParsed and check for if the cursorX === 0, IE the cursor has reset after a write has happened, thus the command has finished.

Repro I used to verify:
Enable NVDA on windows and screen reader mode. Set the default terminal profile to pwsh. Instruct chat agent to run ls in the terminal. Watch it hang and never complete. Same steps using this PR allows it to complete, see screenshot below. Also verified this PR doesn't cause issues when not in screen reader mode. I believe this will fix other peoples' reports too, captured in other issues.

fix #251436

[Tyriar]

Disabled auto merge so I could approve before testing.

[meganrogge]

Closing in favor of #251655