feat(run): show externally started Claude sessions in the active-runs list

The Workspace active-runs list only knew about runs this dashboard spawned,
so two `claude` sessions started by hand in terminal tabs showed up nowhere —
the list read "no active runs" while two agents were working.

Poll GET /api/sessions?status=active alongside the run list and merge those
sessions in as live rows, deduped against dashboard runs by session_id and
filtered to local sources with a cwd (a remote-source or cwd-less session
cannot be resumed on this machine).

External rows get no Attach action: the dashboard owns no tmux session for
them, so there is no PTY to bridge. They offer Resume, which reuses the
existing ensure-lane + start-with-resumeSessionId path to spawn a new
tmux-backed `claude --resume` in that folder — a second process on the same
transcript, not a view of the original terminal.

client/src/components/run/LaneConsolePane.tsx

@@ -4,8 +4,8 @@
  * moved out of Workspace.tsx so the Workspace page can render 1, 2, or 4 of
  * these side by side (split terminal view). Owns its own prompt/cwd/model/
  * permissionMode/effort/resumeSession/handle/busy/runHistory state — nothing
- * is shared between panes. `lanes`, `binaryStatus`, `cwdSuggestions`, and
- * `activeRuns` are supplied as props because they are global, not
+ * is shared between panes. `lanes`, `binaryStatus`, `cwdSuggestions`,
+ * `activeRuns`, and `externalSessions` are supplied as props because they are global, not
  * lane-specific, and fetching them per pane would mean N redundant identical
  * requests for an N-pane layout.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
@@ -38,6 +38,9 @@ export interface LaneConsolePaneProps {
   binaryStatus: { found: boolean; path: string | null } | null;
   cwdSuggestions: CwdSuggestion[];
   activeRuns: RunListResponse | null;
+  /** Active Claude Code sessions started outside the dashboard, listed in the
+   *  active-runs switcher alongside dashboard runs. */
+  externalSessions?: Session[];
   wsConnected: boolean;
   defaultCwd?: string;
   onHasActiveRunChange?: (active: boolean) => void;
@@ -52,6 +55,7 @@ export function LaneConsolePane({
   binaryStatus,
   cwdSuggestions,
   activeRuns,
+  externalSessions,
   wsConnected,
   defaultCwd,
   onHasActiveRunChange,
@@ -340,6 +344,7 @@ export function LaneConsolePane({
           currentHandleId={handle?.id || null}
           onAttach={attachToRun}
           runHistory={runHistory}
+          externalSessions={externalSessions}
           onResumeFromHistory={onResumeFromHistory}
           onViewFromHistory={onViewFromHistory}
           onRefresh={refreshList}