Fix MCP tool call events for Codex MCP

REPORT-codex-mcp-test-hang.md

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+# Codex MCP test hang investigation
+
+## Test that appeared stuck
+- `CodexMcpAgentClient (MCP integration) > maps thread/item events for file changes, MCP tools, web search, and todo lists`
+- Wait loop: `packages/server/src/server/agent/providers/codex-mcp-agent.test.ts:577` (`for await (const event of session.stream(prompt))` until `turn_completed`/`turn_failed`)
+
+## What was actually happening
+- The test was slow (40s+) because the Codex MCP server performed multiple tool call cycles before completing the turn.
+- The run ultimately failed (not a true deadlock) because the MCP tool call timeline item never appeared, so `rawItemTypes.has("mcp_tool_call")` stayed false.
+
+## Root cause
+- Codex MCP server emits `mcp_tool_call_begin` and `mcp_tool_call_end` events with tool invocation + result payloads.
+- `codex-mcp-agent.ts` handled raw_response_item tool calls but ignored `mcp_tool_call_*` events, so MCP tool calls were never mapped to timeline items when those events were the only reliable signal.
+
+## Evidence
+- Observed event shapes from Codex MCP:
+  - `mcp_tool_call_begin` with `call_id` and `invocation` (server/tool/arguments)
+  - `mcp_tool_call_end` with `result.Ok.structuredContent`
+- When mapping those events to tool_call timeline items, the test passed.
+
+## Fix
+- Add schemas + handlers for `mcp_tool_call_begin`/`mcp_tool_call_end` in `packages/server/src/server/agent/providers/codex-mcp-agent.ts`.
+- Emit `tool_call` timeline items for running/completed MCP tool calls and surface structured tool output.