Summary

This PR addresses memory growth and UX issues in long-running Reasonix sessions across three areas: tool card memory optimization (99% string reduction), reasoning state tracking (eliminating the "still thinking" false state), and action button visibility during streaming. It also merges complementary reasoning display improvements from #4318.

1. Tool Memory Optimization

• Archive on tool_result: Every completed tool call is archived immediately — args trimmed to 200 chars (command/subject preview), output dropped entirely. Collapsed cards only hold tool name + command in memory.
• Lazy loading via Wails binding: New Controller.ToolResult() walks Session().Messages by ToolCallID. App.ToolResultForTab exposes it to the frontend. When a card is expanded, full data is fetched on demand.
• History archived on restore: Session history loaded via history action is also archived, not just new turns.
• ToolCard fullData reset on rewind: useEffect cleanup clears cached data when item identity changes.

Tested: 18 unit tests confirm archiving behavior, null-safety, and 99% reduction in tool string data (500-tool session: 7.5M → 100K chars).

Files: internal/control/controller.go, desktop/app.go, useController.ts, ToolCard.tsx, bridge.ts, tool-data-archive.test.ts

2. Reasoning State & Display

• reasoningComplete flag: New LiveStream.reasoningComplete tracks the reasoning→text transition. Auto-closes the reasoning panel as soon as the first text chunk arrives after reasoning, without waiting for message/turn_done.
• expandWhileStreaming (from Fix streaming reasoning UI jank / 修复流式思考过程导致的界面卡顿 #4318): Controls auto-open per display mode. Standard mode auto-expands reasoning; compact mode keeps it collapsed.
• Conditional DOM mounting (from Fix streaming reasoning UI jank / 修复流式思考过程导致的界面卡顿 #4318): {reasoningOpen && <div>} instead of always-mounted CSS-hidden body.
• Streaming truncation (from Fix streaming reasoning UI jank / 修复流式思考过程导致的界面卡顿 #4318): displayReasoningText keeps only the tail (12K chars / 240 lines) while streaming in compact mode.
• Label correctly reflects state: Shows "Thinking completed" instead of "Thinking…" after reasoning finishes but before text output.

Files: Message.tsx, Transcript.tsx, useController.ts, reasoningDisplay.ts, reasoning-display.test.ts

3. Action Button Visibility

Copy/fork/summarize/rewind buttons below each assistant message are hidden while the model is actively generating (state.running === true). Previous completed turns' buttons remain visible with copy enabled. A running prop gates the hot zone's final pushTurnActions().

Files: Transcript.tsx, App.tsx

4. Rendering Performance

Three root-cause fixes for the streaming memory spike (600MB->2GB->600MB):

• LiveAssistantMessage shown in useMemo -> AssistantMessage.memo no longer defeated by new object identity
• Markdown: removed useDeferredValue (caused code-block flicker); normalizeMath in useMemo
• HljsCode: wrapped in React.memo + useMemo — code blocks not re-highlighted when value unchanged
• scrollVersion simplified: {id}:{streaming} / {id}:{status} instead of full length fields
• Auto-scroll coalesced into one requestAnimationFrame per frame (from Fix streaming reasoning UI jank / 修复流式思考过程导致的界面卡顿 #4318)

Files: Transcript.tsx, Markdown.tsx, editors/HljsCode.tsx, render-optimization.test.ts

5. Display Mode Default

Removed "minimal" from DisplayMode. normalizeDisplayMode fallback changed to "standard" to match getDisplayMode.

Files: SettingsPanel.tsx, displayMode.ts, types.ts, config.go

Files Changed

16 files changed, 648 insertions(+), 59 deletions(-)

internal/control/controller.go          +43     # ToolResult() query
desktop/app.go                           +17     # ToolResultForTab binding
desktop/frontend/src/lib/useController.ts +36    # archive + reasoningComplete
desktop/frontend/src/lib/bridge.ts        +4     # AppBindings
desktop/frontend/src/components/ToolCard.tsx +47 # lazy load + fullData reset
desktop/frontend/src/components/Message.tsx +54   # reasoningComplete + #4318 merge
desktop/frontend/src/components/Transcript.tsx +75 # useMemo + running guard + #4318
desktop/frontend/src/components/Markdown.tsx +6   # remove useDeferredValue
desktop/frontend/src/components/editors/HljsCode.tsx +9  # React.memo + useMemo
desktop/frontend/src/components/SettingsPanel.tsx +2    # fix default
desktop/frontend/src/App.tsx              +1     # running prop
desktop/frontend/src/lib/reasoningDisplay.ts +39  # reasoning truncation (#4318)
desktop/frontend/src/__tests__/*          +370   # 3 test files
desktop/frontend/package.json             +4     # test suite

Prefix Cache Invariance

Zero impact. System prompt, tool schemas, session message serialization, and agent Run/Compose paths are untouched. Controller.ToolResult() is a read-only query over Session().Messages — it never mutates history.