insights: make stability explainer more explicit

Explain what the score means: lower = more stable, computed as rolling 6-hour standard deviation normalised to each probe's optimal range. Spikes = rapid deviations from normal conditions.

Commit
f35233630e2cd9125dbe3bb470ca14e8f7083b9c
Author
GPT-5 medium <codex@openai.com>
Author date
Committer
GPT-5 medium <codex@openai.com>
Committer date
roles/dashboard/templates/dashboard/insights.html.ep
index 65230676..8656d8b0 100644..100644
@@ -34,12 +34,15 @@
34 34 <div class="card-header">
35 35 <h3 class="h6 mb-0">System Stability</h3>
36 36 <p class="text-body-secondary small mb-0 mt-1">
37 Removed: Rolling volatility across all probes
37 Added: A <strong>lower score means more stable</strong>.
38 Added: This index is the rolling standard deviation (σ) of all probe values
39 Added: over a 6-hour window, normalised to each probe's optimal range.
40 Added: Spikes indicate rapid or large deviations from normal operating conditions.
38 41 </p>
39 42 </div>
40 43 <div class="card-body">
41 44 <div class="chart-wrap">
42 Removed: <canvas id="chart-stability" role="img" aria-label="System stability score"></canvas>
45 Added: <canvas id="chart-stability" role="img" aria-label="System stability score — lower is better"></canvas>
43 46 </div>
44 47 </div>
45 48 </div>