fix(test): update hydration test to match new structured tool result format

The test was expecting the old 'files' array format, but after the refactor
to structured tool results (commit 4001b7d), Write tools now return:
{ type: 'file_write', filePath, oldContent, newContent }

Updated the test predicate to check for the new structure instead of the
old files array format.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

packages/server/test-results-after.txt

@@ -0,0 +1,16 @@
+
+> @paseo/server@0.1.0 test
+> vitest run
+
+
+ RUN  v3.2.4 /home/moboudra/dev/voice-dev/packages/server
+
+stdout | src/server/agent/providers/codex-agent.test.ts > CodexAgentClient (SDK integration) > responds with text
+[CodexAgentTest] Running single-turn acknowledgment test
+
+stdout | src/server/agent/providers/codex-agent.test.ts > CodexAgentClient (SDK integration) > emits tool or command events when writing a file
+[CodexAgentTest] Streaming file creation activity
+
+stdout | src/server/agent/providers/codex-agent.test.ts > CodexAgentClient (SDK integration) > emits Codex tool calls that hydrate into specific UI entries
+[CodexAgentTest] Streaming Codex run for tool call hydration test
+