fix: bound clipboard channels and coalesce ui notifications

[StudentWeis]

Summary

The clipboard event pipeline in src/app.rs uses async_channel::unbounded for both the clipboard event channel (ClipboardEvent) and the UI notification channel (()). This creates two related issues:

1. Unbounded memory growth under load: Some applications (clipboard managers, paste-heavy IDEs, scripts) write to the clipboard several times per second. With unbounded channels, if the consumer momentarily falls behind (e.g. a slow repo.save_* write or a UI refresh on a large list), pending events can accumulate without limit.
2. Redundant full-list refreshes: Each saved record sends a single () notification, and each notification triggers a full get_display_records(max_history_records) read from the repository plus a full GPUI re-render. Rapid copies fan out into N redundant refreshes when a single coalesced refresh would yield the same UI state.

Steps to Reproduce

1. Launch Ropy.
2. Run a script that writes to the system clipboard 20+ times per second for a few seconds.
3. Observe (via tracing logs / instrumentation) that every event triggers an independent full-list refresh, and that clipboard_rx / notify_rx channel depth can grow unboundedly if the foreground task is briefly stalled.

Expected Behavior

• Both channels are bounded (capacity 256). When full, oldest-style pressure is logged (dropped events for clipboard channel; coalesced/no-op for the notification channel).
• The UI refresh task drains all pending () notifications before doing a single repository read + UI refresh (classic coalescing/debounce pattern).

Actual Behavior

• let (clipboard_tx, clipboard_rx) = async_channel::unbounded::<ClipboardEvent>(); — unbounded.
• let (notify_tx, notify_rx) = async_channel::unbounded::<()>(); — unbounded.
• Every notify_rx.recv().await causes one full get_display_records(...) + GPUI refresh, with no coalescing.

Ropy Version

HEAD of main (pre-fix)

Operating System

All (cross-platform code path in src/app.rs)

Logs / Screenshots

N/A — issue identified by code review (doc/CODE_REVIEW.md §2.1).

Scope

clipboard