docs: fix six cross-task defects found in the UDPScope plan pre-flight

Each of these would have surfaced as a compile/link failure or a reviewer
rejection mid-execution, when the implementer holding the task has no view of
the neighbouring task that contradicts it.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/superpowers/plans/2026-08-27-udpscope.md

@@ -2899,7 +2899,19 @@ TEST(SignalStore, ConcurrentPushAndReadDoNotCrash) {
     }
     stop.store(true);
     writer.join();
-    SUCCEED();
+
+    /* Not just "it did not crash": the store must still be coherent after the
+       race. The window is 0.05 s at 1 MHz, so the ring spans at most
+       0.05 * kRingMargin seconds, and readLast was capped at 4096 points. */
+    double oldest = 0.0, newest = 0.0;
+    ASSERT_TRUE(s.span("a", oldest, newest));
+    EXPECT_GE(newest, oldest);
+    EXPECT_LE(newest - oldest, 0.05 * SignalStore::kRingMargin * 1.5);
+    EXPECT_LE(out.size(), 4096u);
+    EXPECT_EQ(out.t.size(), out.v.size());
+    for (size_t i = 1; i < out.size(); ++i) {
+        EXPECT_GE(out.t[i], out.t[i - 1]) << "timestamps went backwards at " << i;
+    }
 }
 ```
 
@@ -4138,7 +4150,7 @@ TEST(ReceiverLink, StopIsSafeWhenNeverStarted) {
     Receiver rx(store);
     rx.stop();
     EXPECT_FALSE(rx.running());
-    SUCCEED();
+    EXPECT_FALSE(rx.link().running);
 }
 ```
 
@@ -5138,10 +5150,6 @@ void App::drawMenuBar() {
         }
         ImGui::EndMenu();
     }
-    if (ImGui::BeginMenu("View")) {
-        ImGui::MenuItem("(cursors land in Task 13)", nullptr, false, false);
-        ImGui::EndMenu();
-    }
     if (ImGui::BeginMenu("Help")) {
         ImGui::MenuItem("UDPScope — direct UDPS oscilloscope", nullptr, false, false);
         ImGui::EndMenu();
@@ -5974,8 +5982,9 @@ In `Client/udpscope/App.h`, add `#include "PaneView.h"` and the members:
     double   xSpanSec_ = 1.0;   /**< live window width, Task 12 makes it settable */
 ```
 
-In `Client/udpscope/App.cpp`, make the signal list a drag source by replacing
-the `ImGui::Selectable(m.name.c_str());` line with:
+In `Client/udpscope/SignalList.cpp` — that is where Task 9 put
+`App::drawSignalList()`, not `App.cpp` — make the signal list a drag source by
+replacing the `ImGui::Selectable(m.name.c_str());` line with:
 
 ```cpp
         ImGui::Selectable(m.name.c_str());
@@ -6035,10 +6044,14 @@ set(CORE_SOURCES
 set(APP_SOURCES
     main.cpp
     App.cpp
+    SignalList.cpp
     PaneView.cpp
 )
 ```
 
+`SignalList.cpp` stays in the list — it holds `App::drawSignalList()` and
+dropping it is a link error, not a warning.
+
 `PaneView.cpp` needs ImGui headers, so it belongs to the executable, not the
 core library — that is what keeps `udpscope_tests` free of a GUI dependency.
 
@@ -6977,7 +6990,8 @@ and after `paneView_.drawTree(...)`:
     }
 ```
 
-Add the live control to the View menu in `drawMenuBar()`:
+There is no View menu yet — Task 9 built only File and Help. Add one to
+`drawMenuBar()`, between the File and Help blocks:
 
 ```cpp
     if (ImGui::BeginMenu("View")) {
@@ -9169,7 +9183,8 @@ TEST(PaneTree, CloneIsADeepCopy) {
 
 - [ ] **Step 8: Add the File menu and save on exit**
 
-In `App::drawMenuBar()`, before the View menu:
+In `App::drawMenuBar()`, **replace** the File menu block Task 9 wrote (the one
+whose only item is Quit) — do not add a second one:
 
 ```cpp
     if (ImGui::BeginMenu("File")) {