Desktop app: /compact shows no progress indicator (terminal CLI has one)

## Summary

In the Claude Code desktop app (Code tab), `/compact` gives no progress indication. The terminal CLI shows a live progress bar (`Compacting conversation… ▰▰▰▰▱▱▱▱ 21%`, as quoted in #60320); the desktop app renders a single static line and then, some time later, the compacted result.

## Current behavior (desktop app, Code tab)

Invoking `/compact` prints:

```
Compacted
```

That's it — no percentage, no bar, no elapsed indication. On a long session the compaction takes a meaningful amount of time, and during that window there is nothing distinguishing "working" from "wedged". The natural reaction is to wonder whether the command registered at all.

## Expected behavior

The same progress affordance the terminal already has. It exists, it's implemented, and it's the one piece of feedback that makes a slow blocking operation tolerable — it just doesn't surface in the desktop client.

## Why it matters

Compaction is unusual among Claude Code operations: it's blocking, it's slow in proportion to how much context you've accumulated, and it happens precisely at the moment you're deepest into a long session and least willing to lose your place. That's the worst possible time to remove the progress signal.

There's also a secondary parity gap in the same flow, which I'll file separately if it's preferred as its own issue: the terminal lets you export the conversation before compacting and read it back afterwards. The desktop app has no surfaced equivalent. The transcript is on disk as JSONL and can be recovered by hand, so no data is lost — but "shell out and parse JSONL" isn't a feature, and the pre-compaction state is exactly what a user wants to consult after a lossy summarization.

## Environment

- Claude Code 2.1.268
- macOS 26.6.2, arm64
- Desktop app, Code tab (terminal CLI on the same machine shows the progress bar normally)

## Related

- #60320 — closed as duplicate; requested the compaction-style progress bar be extended to tool execution. It documents the terminal compaction UI that this issue is asking the desktop app to match.