Add EGG processing tutorial notebook with Wolpert sample data

First tutorial for GastroPy: a 45-cell Jupyter notebook that walks
through the complete EGG analysis pipeline using real data from
Wolpert et al. (2020). Covers spectral analysis, channel selection,
bandpass filtering, Hilbert phase extraction, cycle detection,
artifact detection, quality metrics, and multi-band analysis.
All outputs pre-computed and embedded for Sphinx rendering.

Author: micahgallen

README.md

@@ -157,6 +157,16 @@ phases = apply_volume_cuts(phases, begin_cut=21, end_cut=21)
 fig, ax = gp.plot_volume_phase(phases, tr=1.856, cut_start=21, cut_end=21)
 ```
 
+## Tutorials
+
+Learn EGG processing from scratch with our step-by-step tutorial using real
+data from Wolpert et al. (2020):
+
+- **[EGG Signal Processing](https://embodied-computation-group.github.io/gastropy/tutorials/egg_processing.html)** —
+  Load multi-channel EGG data, compute PSD, select the best channel, bandpass
+  filter, extract phase and amplitude, detect artifacts, compute quality
+  metrics, and run multi-band analysis. No prior EGG experience needed.
+
 ## Documentation
 
 Full API reference and tutorials at

docs/getting_started.rst

@@ -197,6 +197,9 @@ normogastria, tachygastria) for per-band metrics.
 What's Next
 -----------
 
+For a hands-on walkthrough using real EGG data, see the
+:doc:`EGG Signal Processing Tutorial <tutorials/egg_processing>`.
+
 GastroPy is under active development. Upcoming modules include
 gastric-brain phase coupling, data I/O with BIDS support, and
 statistical testing. See the :doc:`API Reference <api/index>`

docs/tutorials/egg_processing.ipynb

@@ -1,13 +1,10 @@
 Tutorials
 =========
 
-Tutorials will be added here as GastroPy modules are implemented.
-Each tutorial is a Jupyter notebook demonstrating a specific aspect
-of the EGG processing pipeline.
+Step-by-step guides demonstrating how to use GastroPy for EGG signal
+processing and analysis.
 
-.. Planned tutorials:
-   - Loading and inspecting EGG data
-   - EGG signal preprocessing
-   - Time-frequency analysis of gastric rhythm
-   - Computing EGG metrics
-   - Gastric-brain coupling with fMRI
+.. toctree::
+   :maxdepth: 2
+
+   egg_processing