feat: introduce MessageGroup model replacing flat Message[] for grouped assistant rendering

[genni613]

User description

Summary

• 引入 MessageGroup[] 替代扁平 Message[] 渲染模型，将执行卡片和最终回答归入同一 assistant 组
• 消除后端 bridgeNotifiedStart / notifyRemoveMessage 排序 hack，改为无条件的 notifyStart + notifyRoundEnd

Changes

• 新增 groupReducer.ts 替代 eventReducer.ts，用 GroupState + MessageGroup 管理状态
• 新增 AssistantGroup.tsx、AssistantMarkdown.tsx 组件，分别渲染分组和 markdown
• 更新 App.tsx：从 messages[] 切换到 groups[]，简化加载指示器（仅在无流式文本时显示 spinner）
• 简化 ChatService.kt：移除 bridgeNotifiedStart 集合，startStreamingRound() 无条件发送 notifyStart，onFinishReason("tool_calls") 改发
  notifyRoundEnd
• 新增 29 个 groupReducer 测试用例（含工具调用流程、多轮执行、会话恢复等场景）

Test plan

• 65 个前端测试全部通过（含 29 个新增 groupReducer 测试）
• 工具调用流程：执行卡片在最终文本之前，中间 token 被 round_end 正确丢弃
• 多轮工具调用：正确分组在同一个 assistant 组内
• 执行卡片自动折叠：运行时展开，完成后自动折叠
• 会话恢复：历史消息正确转换为分组结构
• 正文流式输出时底部不显示多余 spinner

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PR Type

Enhancement

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Description

• Replace flat Message[] with MessageGroup[] for grouped assistant rendering (execution cards + final answer in same group)

• Remove backend bridgeNotifiedStart hack; send unconditional notifyStart + notifyRoundEnd for token discarding

• Add groupReducer.ts with GroupState, AssistantGroup, HumanGroup types; handle 'round_end' to discard intermediate tokens

• Add AssistantGroup.tsx and AssistantMarkdown.tsx components; update App.tsx to use groups and simplify spinner logic

• Add 29 groupReducer tests covering tool calls, multi-round flows, session restore

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Diagram Walkthrough

flowchart LR
  A[Kotlin ChatService] -->|"notifyStart"| B[Frontend groupReducer]
  A -->|"notifyToken"| B
  A -->|"execution_card"| B
  A -->|"notifyRoundEnd"| B
  B --> C[GroupState with groups[]]
  C --> D[AssistantGroup component]
  C --> E[HumanGroup component]

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File Walkthrough

	Relevant files
Enhancement	5 files ChatService.kt Remove bridgeNotifiedStart hack, add notifyRoundEnd            +14/-44  App.tsx Switch from messages[] to groups[] with groupReducer          +29/-22  AssistantGroup.tsx New component for grouped assistant rendering                        +81/-0    AssistantMarkdown.tsx New component for markdown rendering with code highlighting +83/-0    groupReducer.ts New reducer with GroupState and MessageGroup types              +255/-0
Documentation	1 files unified-tool-design.md Update design doc for Phase 2 MessageGroup architecture    +157/-57
Configuration changes	2 files package.json Add groupReducer test to test script                                          +1/-1      tsconfig.test.json Add groupReducer.ts to test build include                                +2/-1
Tests	1 files groupReducer.test.mjs New test file with 29 groupReducer test cases                        +436/-0
Additional files	1 files index.html +60/-60

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[github-actions]

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[github-actions]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
General	Use crypto.randomUUID() instead of Date.now() for unique IDs Using Date.now() for text child IDs can cause collisions if multiple rapid tokens arrive within the same millisecond. Consider using a counter or UUID for unique IDs. webview/src/groupReducer.ts [90-111] case 'token': { const lastGroup = state.groups[state.groups.length - 1] if (lastGroup?.type !== 'assistant') return state const group = lastGroup as AssistantGroup - let newTextIndex = state.currentRoundTextIndex + const newTextIndex = state.currentRoundTextIndex if (newTextIndex !== null && group.children[newTextIndex]?.kind === 'text') { const existing = group.children[newTextIndex] as AssistantChild & { kind: 'text' } const updated = [...group.children] updated[newTextIndex] = { kind: 'text', id: existing.id, content: existing.content + payload.text, isStreaming: existing.isStreaming } const groups = [...state.groups] groups[groups.length - 1] = { ...group, children: updated } return { ...state, groups } } - const textChild: AssistantChild = { kind: 'text', id: `text-${Date.now()}`, content: payload.text, isStreaming: true } - newTextIndex = group.children.length + const textChild: AssistantChild = { kind: 'text', id: `text-${crypto.randomUUID()}`, content: payload.text, isStreaming: true } + const appendIndex = group.children.length const groups = [...state.groups] groups[groups.length - 1] = { ...group, children: [...group.children, textChild] } - return { ...state, groups, currentRoundTextIndex: newTextIndex } + return { ...state, groups, currentRoundTextIndex: appendIndex } } Suggestion importance[1-10]: 4 __ Why: The suggestion correctly identifies a potential ID collision issue with Date.now(). While the practical risk is low (tokens arrive rapidly within the same round and are appended sequentially), using crypto.randomUUID() provides more robust uniqueness guarantees. This is a minor improvement to code quality rather than a critical bug fix.	Low