Add workspace index and developer-specific journals for AI sessions

- Created a main workspace index to track AI Agent work records across developers.
- Added a personal index for developer 'yuxuanhui' with current status and session history.
- Initialized the first journal file for 'yuxuanhui' to document AI development sessions.
- Introduced AGENTS.md for Trellis instructions, detailing project structure and usage guidelines.

.codex/hooks.json

@@ -0,0 +1,27 @@
+{
+  "hooks": {
+    "UserPromptSubmit": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 -X utf8 .codex/hooks/inject-workflow-state.py",
+            "timeout": 15
+          }
+        ]
+      }
+    ],
+    "SubagentStart": [
+      {
+        "matcher": "^(?:trellis-implement|trellis-check|trellis-research)$",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 -X utf8 .codex/hooks/inject-subagent-context.py",
+            "timeout": 15
+          }
+        ]
+      }
+    ]
+  }
+}