fix: collapse additional-stations list by default; no scroll-jump on station click

The 97-row ThaiWater/HII list was starving the RID flow list down to one
visible row. The section header is now a click/keyboard toggle (collapsed
by default, arrow indicator); searching auto-expands it so hidden
stations stay findable, and the flow list keeps a 280px minimum when
both are open. Selecting a station no longer scrollIntoViews the
history card.

src/static/dashboard.html

@@ -89,7 +89,10 @@
         .side-head { padding: 18px 18px 14px; border-bottom: 1px solid var(--border); }
         .side-head h2 { margin: 0; font-size: 1rem; }
         .side-head p { margin: 5px 0 0; color: var(--muted); font-size: .75rem; }
-        .station-list { overflow-y: auto; padding: 7px; }
+        .station-list { overflow-y: auto; padding: 7px; min-height: 0; }
+        /* The RID flow list keeps at least ~5 rows even with the sensor list expanded */
+        #river-flow { flex: 1 1 auto; min-height: 280px; }
+        #thaiwater-sensors { flex: 1 1 auto; }
         .station-row {
             width: 100%; display: grid; grid-template-columns: 40px minmax(0,1fr) auto; gap: 10px; align-items: center;
             padding: 11px; border: 0; border-radius: 12px; box-shadow: none; text-align: left; background: transparent;
@@ -238,8 +241,8 @@
                 <input type="search" id="station-search" placeholder="Search stations · code, name, river…" aria-label="Search stations" style="margin-top:10px;width:100%;box-sizing:border-box;padding:9px 12px;border:1px solid var(--border);border-radius:10px;background:white;font-size:.8rem">
             </div>
             <div class="station-list" id="river-flow" aria-live="polite"></div>
-            <div class="side-head"><h2>Additional basin stations</h2><p id="thaiwater-count">Loading ThaiWater/HII stations…</p></div>
+            <div class="side-head" id="sensors-head" style="cursor:pointer" role="button" tabindex="0" title="Show / hide the ThaiWater/HII station list"><h2>Additional basin stations <span id="sensors-arrow" style="color:var(--muted);font-size:.8rem">▸</span></h2><p id="thaiwater-count">Loading ThaiWater/HII stations…</p></div>
-            <div class="station-list" id="thaiwater-sensors" aria-live="polite"></div>
+            <div class="station-list" id="thaiwater-sensors" aria-live="polite" style="display:none"></div>
         </aside>
     </section>
 
@@ -619,16 +622,22 @@
                 }]
             });
             $('history-status').textContent = rows.length ? `${rows.length} measurements${sampled.length !== rows.length ? ` (${sampled.length} daily averages)` : ''}` : 'No measurements in this period';
-            $('history-card').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
         } catch (error) {
             $('history-status').textContent = `History unavailable: ${error.message}`;
         }
     }
 
+    function setSensorsOpen(open) {
+        state.sensorsOpen = open;
+        $('thaiwater-sensors').style.display = open ? '' : 'none';
+        $('sensors-arrow').textContent = open ? '▾' : '▸';
+    }
+
     // Filters both station lists by any text on the row (code, names, river —
     // Thai included, since it matches against the rendered text).
     function applyStationSearch() {
         const query = $('station-search').value.trim().toLowerCase();
+        if (query && !state.sensorsOpen) setSensorsOpen(true); // search reaches hidden stations
         ['river-flow', 'thaiwater-sensors'].forEach((id) => {
             [...$(id).children].forEach((row) => {
                 row.style.display = !query || row.textContent.toLowerCase().includes(query) ? '' : 'none';
@@ -1174,6 +1183,10 @@
             : `Show all ${count} station forecasts ▾`;
     });
     $('station-search').addEventListener('input', applyStationSearch);
+    $('sensors-head').addEventListener('click', () => setSensorsOpen(!state.sensorsOpen));
+    $('sensors-head').addEventListener('keydown', (event) => {
+        if (event.key === 'Enter' || event.key === ' ') { event.preventDefault(); setSensorsOpen(!state.sensorsOpen); }
+    });
     $('rain-toggle').addEventListener('change', (event) => {
         if (!state.rainLayer) return;
         if (event.target.checked) state.rainLayer.addTo(state.map);