COD-130 session-row ⋯ becomes a context menu

The per-row ⋯ in the session list was a details toggle that did nothing in
the Session Manager modal (swallowed by the modal's capture-phase
close-on-click). Replace it with a real kebab context menu.

- terminal-ui.js: ⋯ now opens _openSessionRowMenu() — a body-anchored popup
  (fixed-positioned, flips/clamps to viewport, z-index above the modal) with:
  Resume/Switch-to (live→select tab, closed→resume), Open folder in the file
  browser (live sessions only — the browser is session-scoped), Copy path
  (_copyText + toast, when workingDir present), and Show details (the old
  inline prompt/path panel). Closes on outside-click / Escape / scroll / resize.
- panels-ui.js: _loadSessionManagerList scopes its modal-close to the
  .history-item-main (resume) click, so the ⋯/menu no longer closes the modal.
- styles.css: .session-row-menu + .session-row-menu-item.

Verified in Chromium on an isolated beta: ⋯ opens the menu with the modal
still open; closed rows show Resume/Copy path/Show details, live rows add
Switch-to + Open folder; Show details expands inline (modal stays open),
Copy path copies the path, Resume closes the modal, Escape closes only the
menu. Gates: tsc 0, lint 0, frontend-syntax + public-asset format clean.

src/web/public/styles.css

@@ -5471,6 +5471,51 @@ kbd {
   overflow-y: auto;
 }
 
+/* COD-130: per-row ⋯ kebab context menu (appended to <body>, fixed-positioned).
+   z-index must clear the Session Manager modal (.modal is z-index: 1000). */
+.session-row-menu {
+  position: fixed;
+  z-index: 10010;
+  min-width: 180px;
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  padding: 4px;
+  background: rgba(22, 22, 28, 0.97);
+  backdrop-filter: blur(20px);
+  -webkit-backdrop-filter: blur(20px);
+  border: 1px solid var(--border);
+  border-radius: 10px;
+  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.5), 0 2px 8px rgba(0, 0, 0, 0.3);
+}
+
+.session-row-menu-item {
+  display: flex;
+  flex-direction: column;
+  align-items: flex-start;
+  gap: 1px;
+  width: 100%;
+  padding: 7px 12px;
+  background: none;
+  border: none;
+  border-radius: var(--btn-radius);
+  color: var(--text);
+  cursor: pointer;
+  font-size: 0.8rem;
+  text-align: left;
+  white-space: nowrap;
+  transition: background var(--transition-smooth);
+}
+
+.session-row-menu-item:hover {
+  background: var(--bg-hover);
+}
+
+.session-row-menu-sublabel {
+  color: var(--text-muted);
+  font-size: 0.72rem;
+}
+
 .away-digest-ranges {
   display: flex;
   flex-wrap: wrap;