[Feature]: Add sweep/decompress/recompress action buttons to TUI panel

[Gedof]

Problem

Due to the sentinel error bug in v3.1.12 (see #570), I had to upgrade to v3.1.13. However, v3.1.13 removed the /dcp sweep, /dcp decompress, and /dcp recompress slash subcommands, while the new TUI panel only exposes Context view, Stats view, and Manual Mode toggle. There is no user-facing way to manually trigger a sweep or manage decompressions/recompressions — those operations are only available through the LLM-controlled compress tool.

Proposed Solution

Add action buttons to the TUI PanelDialog for:

• Sweep — trigger a manual sweep (optionally with a configurable count / last N tools)
• Decompress — list past compressions and select one to restore
• Recompress — re-apply a previously decompressed entry

These would mirror the functionality that /dcp sweep, /dcp decompress, and /dcp recompress provided in v3.1.12.

Alternatives Considered

• Keeping the slash subcommands alongside the TUI panel (would maybe require routing /dcp exclusively to the TUI, with separated config commands like /dcp-sweep, /dcp-decompress for the server-side handlers)
• Relying only on DCP's auto-sweep pipeline (no manual control)
• Staying on v3.1.12 with the sentinel error (broken UI, see [Bug]: /dcp subcommands throw sentinel errors visible to users as unhandled exceptions #570)

Additional Context

• opencode 1.17.9
• DCP 3.1.13