feat(notebooks): Add Jupytext + Papermill agent workflow demo

- Add parameterized system-health notebook (.py source + .ipynb)
- Add Gitea Actions CI workflow for notebook execution smoke test
- Add NOTEBOOK_WORKFLOW.md documenting the .py-first approach
- Proves end-to-end: agent writes .py -> PR review -> CI executes -> output artifact

docs/NOTEBOOK_WORKFLOW.md

@@ -0,0 +1,57 @@
+# Notebook Workflow for Agent Tasks
+
+This directory demonstrates a sovereign, version-controlled workflow for LLM agent tasks using Jupyter notebooks.
+
+## Philosophy
+
+- **`.py` files are the source of truth`** — authored and reviewed as plain Python with `# %%` cell markers (via Jupytext)
+- **`.ipynb` files are generated artifacts** — auto-created from `.py` for execution and rich viewing
+- **Papermill parameterizes and executes** — each run produces an output notebook with code, narrative, and results preserved
+- **Output notebooks are audit artifacts** — every execution leaves a permanent, replayable record
+
+## File Layout
+
+```
+notebooks/
+  agent_task_system_health.py      # Source of truth (Jupytext)
+  agent_task_system_health.ipynb   # Generated from .py
+docs/
+  NOTEBOOK_WORKFLOW.md             # This document
+.gitea/workflows/
+  notebook-ci.yml                  # CI gate: executes notebooks on PR/push
+```
+
+## How Agents Work With Notebooks
+
+1. **Create** — Agent generates a `.py` notebook using `# %% [markdown]` and `# %%` code blocks
+2. **Review** — PR reviewers see clean diffs in Gitea (no JSON noise)
+3. **Generate** — `jupytext --to ipynb` produces the `.ipynb` before merge
+4. **Execute** — Papermill runs the notebook with injected parameters
+5. **Archive** — Output notebook is committed to a `reports/` branch or artifact store
+
+## Converting Between Formats
+
+```bash
+# .py -> .ipynb
+jupytext --to ipynb notebooks/agent_task_system_health.py
+
+# .ipynb -> .py
+jupytext --to py notebooks/agent_task_system_health.ipynb
+
+# Execute with parameters
+papermill notebooks/agent_task_system_health.ipynb output.ipynb \
+  -p threshold 1.0 -p hostname forge-vps-01
+```
+
+## CI Gate
+
+The `notebook-ci.yml` workflow executes all notebooks in `notebooks/` on every PR and push, ensuring that checked-in notebooks still run and produce outputs.
+
+## Why This Matters
+
+| Problem | Notebook Solution |
+|---|---|
+| Ephemeral agent reasoning | Markdown cells narrate the thought process |
+| Stateless single-turn tools | Stateful cells persist variables across steps |
+| Unreviewable binary artifacts | `.py` source is diffable and PR-friendly |
+| No execution audit trail | Output notebook preserves code + outputs + metadata |