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.

.agents/skills/trellis-meta/references/customize-local/change-spec-structure.md

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+# Change Local Spec Structure
+
+When the user wants to change the engineering conventions AI follows, add new spec layers, or adjust monorepo package mapping, edit `.trellis/spec/` and `.trellis/config.yaml`.
+
+## Read These Files First
+
+1. `.trellis/config.yaml`
+2. `.trellis/spec/`
+3. `.trellis/workflow.md` planning artifact guidance and Phase 3.3
+4. Current task `implement.jsonl` / `check.jsonl`
+
+## Common Needs
+
+| Need | Edit location |
+| --- | --- |
+| Add backend/frontend/docs/test spec layer | `.trellis/spec/<layer>/` or `.trellis/spec/<package>/<layer>/` |
+| Add shared thinking guides | `.trellis/spec/guides/` |
+| Adjust monorepo packages | `packages` in `.trellis/config.yaml` |
+| Change default package | `default_package` in `.trellis/config.yaml` |
+| Control spec scanning scope | `spec_scope` in `.trellis/config.yaml` |
+| Make a task read a new spec | Task `implement.jsonl` / `check.jsonl` |
+
+## Add A Spec Layer
+
+Single-repository example:
+
+```text
+.trellis/spec/security/
+├── index.md
+└── auth.md
+```
+
+Monorepo example:
+
+```text
+.trellis/spec/webapp/security/
+├── index.md
+└── auth.md
+```
+
+`index.md` should include:
+
+- What code this layer applies to.
+- Pre-Development Checklist.
+- Quality Check.
+- Links to specific guideline files.
+
+## Update Context
+
+Adding a spec does not mean every task automatically reads it. The current task must reference it in JSONL:
+
+```bash
+python3 ./.trellis/scripts/task.py add-context <task> implement ".trellis/spec/webapp/security/index.md" "Security conventions"
+python3 ./.trellis/scripts/task.py add-context <task> check ".trellis/spec/webapp/security/index.md" "Security review rules"
+```
+
+## Change Monorepo Packages
+
+Example `.trellis/config.yaml`:
+
+```yaml
+packages:
+  webapp:
+    path: apps/web
+  api:
+    path: apps/api
+default_package: webapp
+```
+
+After editing, run:
+
+```bash
+python3 ./.trellis/scripts/get_context.py --mode packages
+```
+
+Use this output to confirm AI can see the correct packages and spec layers.
+
+## Notes
+
+- Specs are user project conventions and can be changed according to project needs.
+- Do not put temporary task information into specs; put temporary information in the task.
+- Do not put long-term conventions only in agents or commands; preserve them in specs.
+- After changing spec structure, check whether existing task JSONL files still point to files that exist.