Plan mode re-renders full plan on every notification even when entries are unchanged

[tarushnagpal]

Checklist

• I agree to communicate with the author myself (not AI-generated).
• I've read the README's Filing issues section.
• I'm running the latest versions (fill in below).
  • agent-shell version: 0.50.1
  • acp.el version: 0.11.2
  • ACP package (e.g. claude-agent-acp) version: 0.50.1
  • Agent CLI (e.g. claude, gemini) version: Claude Code 2.1.81
• For requesting new agent support, I'm including a link to the ACP-capable agent or related ACP package.
• For issues, I'm including ACP traffic (as per README).

Description

When in plan mode and asking a normal question that doesn't update the plan, the full plan is still rendered in the output. This makes the response noisy, The entire plan block gets displayed even though nothing in it changed.

Expected behavior

If the plan entries haven't changed between notifications, the plan block should not be re-displayed in the output.

Actual behavior

Every "plan" sessionUpdate notification unconditionally calls agent-shell--update-fragment and renders the full plan, regardless of whether the plan content is identical to what was already shown.