feat(trajectory): implement trajectory step cell and layout with bilingual support

- Added TrajectoryCell, TrajectoryGroupHeader, and TrajectoryTurn components for rendering trajectory steps and groups.
- Introduced bilingual support with English and Chinese translations for trajectory notes.
- Updated conversation session models to include timestamps for various message types.
- Enhanced layout logic to handle expanded assistant blocks and tool results with duration metrics.
- Added CSS styles for new components to ensure proper display and alignment.

packages/client/ui-conversation/tests/chat-stats-bash-sample.spec.tsx

@@ -20,7 +20,7 @@ afterEach(cleanup)
 const SID = 's1' as SessionId
 
 const assistant = (seq: number, turn: number, usage?: unknown): AssistantMessageNode => ({
-  kind: 'assistant', seq, turn, step: seq, blocks: [{ kind: 'text', text: `t${seq}` }],
+  kind: 'assistant', seq, time: seq * 1_000, turn, step: seq, blocks: [{ kind: 'text', text: `t${seq}` }],
   ...(usage === undefined ? {} : { usage }),
 })
 
@@ -65,7 +65,7 @@ describe('deriveStats', () => {
 
   it('cache hit stays null with no cache accounting; non-assistant nodes ignored', () => {
     const tool: ToolResultNode = {
-      kind: 'tool-result', seq: 5, callId: 'c', call: null, content: [],
+      kind: 'tool-result', seq: 5, time: 5_000, callId: 'c', call: null, callTime: null, content: [],
       isError: false, callView: null, resultView: null,
     }
     const stats = deriveStats([tool, assistant(1, 1)])
@@ -112,8 +112,9 @@ describe('bash sample row', () => {
   const CHILD = 'child-1' as SessionId
 
   const result = (callId: string): ToolResultNode => ({
-    kind: 'tool-result', seq: 3, callId,
+    kind: 'tool-result', seq: 3, time: 3_000, callId,
     call: { name: 'bash', argsRaw: '{"command":"make build","description":"Build"}' },
+    callTime: 2_000,
     content: [], isError: false, callView: null, resultView: null,
   })