Sig Select: regression spec — re-ready restarts the visual countdown (client bisection)

A diagnostic that replays the reported "cancel → re-ready doesn't restart the
flashing numeral" sequence purely through the client handlers (countdown_start →
countdown_cancel → countdown_start). It passes: _showCountdown re-renders the
numeral every time the event is received, so the client logic is sound.

This bisects the live bug to WS *delivery* (the re-ready countdown_start not
reaching the browser), not client state — consistent with a dropped room socket
that never reconnected (every subsequent live event lost until a refresh, which
matches the symptom exactly). The auto-reconnect added in a6ce207 is the
relevant mitigation; kept as a permanent guard on the client restart path.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/static/tests/SigSelectSpec.js

@@ -919,6 +919,25 @@ describe("SigSelect", () => {
             takeSigBtn = document.getElementById("id_take_sig_btn");
             expect(takeSigBtn.textContent).toBe("WAIT NVM");
         });
+
+        it("re-renders the numeral when countdown_start arrives again after a cancel", () => {
+            // Diagnostic for the re-ready bug: cancel → re-ready must restart the
+            // visual countdown. This exercises the CLIENT handler chain only; if
+            // it passes, the live failure is WS delivery (socket / broadcast), not
+            // client logic.
+            makeFixture({ reservations: '{"42":"PC"}', ready: true, countdownRemaining: 9 });
+            takeSigBtn = document.getElementById("id_take_sig_btn");
+            expect(takeSigBtn.textContent).toBe("9");                       // counting
+            window.dispatchEvent(new CustomEvent("room:countdown_cancel", {
+                detail: { polarity: "levity", seconds_remaining: 7 },
+            }));
+            expect(takeSigBtn.textContent).toBe("WAIT NVM");                // cancelled
+            window.dispatchEvent(new CustomEvent("room:countdown_start", {
+                detail: { polarity: "levity", seconds: 7 },
+            }));
+            expect(takeSigBtn.textContent).toBe("7");                       // restarted
+            expect(takeSigBtn.classList.contains("sig-take-sig-btn--counting")).toBe(true);
+        });
     });
 
     // ── polarity_room_done → tray sequence ─────────────────────────────────── //

src/static_src/tests/SigSelectSpec.js

@@ -919,6 +919,25 @@ describe("SigSelect", () => {
             takeSigBtn = document.getElementById("id_take_sig_btn");
             expect(takeSigBtn.textContent).toBe("WAIT NVM");
         });
+
+        it("re-renders the numeral when countdown_start arrives again after a cancel", () => {
+            // Diagnostic for the re-ready bug: cancel → re-ready must restart the
+            // visual countdown. This exercises the CLIENT handler chain only; if
+            // it passes, the live failure is WS delivery (socket / broadcast), not
+            // client logic.
+            makeFixture({ reservations: '{"42":"PC"}', ready: true, countdownRemaining: 9 });
+            takeSigBtn = document.getElementById("id_take_sig_btn");
+            expect(takeSigBtn.textContent).toBe("9");                       // counting
+            window.dispatchEvent(new CustomEvent("room:countdown_cancel", {
+                detail: { polarity: "levity", seconds_remaining: 7 },
+            }));
+            expect(takeSigBtn.textContent).toBe("WAIT NVM");                // cancelled
+            window.dispatchEvent(new CustomEvent("room:countdown_start", {
+                detail: { polarity: "levity", seconds: 7 },
+            }));
+            expect(takeSigBtn.textContent).toBe("7");                       // restarted
+            expect(takeSigBtn.classList.contains("sig-take-sig-btn--counting")).toBe(true);
+        });
     });
 
     // ── polarity_room_done → tray sequence ─────────────────────────────────── //