Merge PR #146 from aakhter/cod-163-command-palette: searchable case picker + Command-K session palette

Includes review fixes: Session Manager aligned to the merged /api/sessions/unified contract with error states, Ctrl+K no longer leaks 0x0B into the PTY, shortcut registry finished (dispatch/persistence/rendering), shortcutOverrides preserved across settings saves, help modal kept reachable.

# Conflicts:
#	README.md
#	src/web/public/index.html
#	src/web/public/session-ui.js

src/web/public/mobile.css

@@ -162,7 +162,11 @@ html.mobile-init .file-browser-panel {
   }
 
   .case-select-group {
-    max-width: 150px;
+    max-width: none;
+  }
+
+  .case-combobox {
+    width: 160px;
   }
 
   .toolbar-select {
@@ -194,6 +198,27 @@ html.mobile-init .file-browser-panel {
     z-index: 1300;
   }
 
+  .command-palette-modal {
+    padding: 10vh 0.75rem 0;
+  }
+
+  .command-palette-shell {
+    width: 100%;
+    max-height: 74vh;
+  }
+
+  .command-palette-input-row {
+    grid-template-columns: 20px minmax(0, 1fr);
+  }
+
+  .command-palette-input-row kbd {
+    display: none;
+  }
+
+  .command-palette-item {
+    min-height: 56px;
+  }
+
   .modal-tabs {
     overflow-x: auto;
     -webkit-overflow-scrolling: touch;