fix: correct global coherence plotting for Nyquist frequency fix

The Nyquist frequency fix changed how frequencies are returned:
- connectivity.frequencies now includes the Nyquist frequency (N//2+1 freqs)
- global_coherence() returns data for ALL frequencies (both +/-)

Updated the global coherence plotting code to:
1. Extract first N//2+1 frequencies from global_coherence
2. Use connectivity.frequencies directly (no manual Nyquist append)
3. Add proper edge for pcolormesh grid to match data dimensions

This fixes the pcolormesh dimension mismatch error.

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

Co-Authored-By: Claude <[email protected]>

Author: edeno

examples/Tutorial_On_Simulated_Examples.ipynb

@@ -2424,16 +2424,21 @@
 
 global_coherence, unnormalized_global_coherence = connectivity.global_coherence()
 print(global_coherence.shape)  # n_time, n_frequencies, n_components
+
+# Extract non-negative frequencies (first N//2+1 frequencies)
+n_nonneg_freqs = len(connectivity.frequencies)
+global_coherence_nonneg = global_coherence[:, :n_nonneg_freqs, 0].T  # (freqs, time)
+
 time_grid, freq_grid = np.meshgrid(
     np.append(connectivity.time, time_extent[-1]),
-    np.append(connectivity.frequencies, multitaper.nyquist_frequency),
+    np.append(connectivity.frequencies, connectivity.frequencies[-1]),  # Add edge for pcolormesh
 )
 plt.figure()
 plt.pcolormesh(
     time_grid,
     freq_grid,
-    global_coherence[:, connectivity.all_frequencies >= 0, 0].T,
-    shading="auto",
+    global_coherence_nonneg,
+    shading="flat",
 )
 plt.title("Global Coherence (1st component)")
 plt.xlabel("Time [s]")