feat: compact tool pill UI with auto-grouping

[dimakis]

Summary

Replaces the bulky tool call cards (which dominated the viewport on mobile) with compact single-line pills that auto-group.

Before: Each tool call was a multi-line card taking ~3+ lines. 8 Read calls = entire screen filled with cards, no visible response.

After:

• Individual pills: [dot] Read server/chat.ts — one line. Shows "Running..." while active, fades to green dot when done. Tap to expand for full input/result.
• Auto-grouping: 3+ consecutive tool calls collapse into a single row: [dots] 5 tool calls [v]. Tap to expand.
• Smart state: Groups stay expanded while tools are running, auto-collapse when all finish.
• Text messages break grouping, so you always see Claude's responses immediately.

Test plan

• Start a chat that triggers multiple tool calls (e.g., "what files are in this repo?")
• Verify individual tool calls show as compact pills, not cards
• Verify 3+ consecutive calls collapse into a group
• Verify group expands on tap, shows individual pills inside
• Verify group auto-collapses when all tools finish
• Verify tapping a done pill expands to show the result
• Verify text messages appear between tool groups correctly

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