fix #371: straddling rows clip at the viewport edge instead of vanishing whole

Gate-3 screenshot review (user): 'the chat tab looks like it is missing
per window config' — Chat Window 1's header rendered over a void at the
DEFAULT scroll offset because its 260px self-sized filter block
straddled the viewport's bottom edge and UiScrollablePanel hid
straddling rows WHOLE (AP-201's predicted symptom, now user-observed at
scroll position zero, upgrading it from polish to blocking).

By fix time the UI renderer HAD everything needed: UiRenderContext's
clip stack (PushClip/PopClip with rect intersection + per-draw quad
clipping) and UiElement's ClipsChildren hook, already honored by both
the generic draw walk and hit-testing. The fix is therefore exactly the
shape the filing asked for, in the panel itself:
- ClipsChildren => true: children draw and hit-test clipped to the
  viewport rect.
- The layout cull keeps any INTERSECTING row Visible (was: fully-inside
  only), with a half-pixel margin excluding zero-overlap edge rows;
  fully-outside rows stay hidden as the cheap skip.

AP-201 retired in this commit (AP actives 142 -> 141); #371 closed; the
gate script's Chat-tab steps re-written to expect clean edge clipping
and to treat any whole-block vanish as a regression. Pinned by
StraddlingRow_StaysVisible_AndClipsInsteadOfVanishing (the exact gate-3
geometry: header + 260px straddler in a 430px viewport) and
ViewportClipsChildDrawingAndHitTesting (the clipped slice is not
clickable).

Full Release suite: 13,089 passed / 4 skipped / 0 failed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/ISSUES.md

@@ -24,6 +24,26 @@ What does NOT go here:
 - Every session: scan OPEN issues at start; promote/close anything we touched during the session before ending.
 - Promoting to a Phase: mark as `DONE (promoted to Phase X)` + commit SHA where the Phase entry landed.
 
+## #377 — Startup CRASH (0xC0000005 in Glfw.GetVideoMode) when settings.json has `fullscreen: true`
+
+**Status:** OPEN — filed 2026-08-11. Reproduced deterministically on this
+machine: with the persisted display settings carrying `fullscreen: true`
+(left behind by #374's stolen dropdown click during gate 2), the client
+dies during `GameWindow.OnLoad` → `GameWindowCompositionPipeline.Run` →
+`Silk.NET.GLFW.Glfw.GetVideoMode(Monitor*)` with an access violation —
+a native AV, not a managed exception, so no graceful error path runs.
+Windowed startup (`fullscreen: false`) is unaffected. Likely site:
+`DisplayFramePacingController` reading `_window.Monitor?.VideoMode`
+(`src/AcDream.App/Rendering/DisplayFramePacingController.cs:35`) while
+the window is mid-fullscreen-transition (or `Monitor` returning a
+non-null but invalid handle in that state) — to CONFIRM, not assume.
+Root-cause before fixing; the fix must make fullscreen startup safe, not
+suppress the read (no workarounds rule). Until then: a user whose
+settings carry `fullscreen: true` cannot launch — workaround is editing
+settings.json back to `false` by hand. Related: #376 (fullscreen video-
+mode switching), #374 (how the value got corrupted — that entry path is
+fixed).
+
 ## #376 — Fullscreen resolution picks cannot switch the display mode (Silk API limit; needs native glfwSetWindowMonitor)
 
 **Status:** OPEN — filed 2026-08-11, split from #374's investigation.
@@ -240,7 +260,23 @@ can never regress green again.
 
 ## #371 — Options-panel row viewport culls whole rows instead of clipping; tall filter blocks can vanish entirely at some scroll offsets
 
-**Status:** OPEN — filed 2026-08-11 at the OP5 review-fix round (S2).
+**Status:** DONE — fixed 2026-08-11 at the Campaign OP gate-3 fix round.
+The user's gate-3 screenshot review caught the predicted symptom at the
+DEFAULT scroll offset ("the chat tab looks like it is missing per window
+config" — Chat Window 1's header rendered over a void, its 260px filter
+block whole-row-culled, windows 2-4 below the fold). By fix time the UI
+renderer HAD grown a clip stack (`UiRenderContext.PushClip`, already
+honored by the generic draw walk and hit-test via `ClipsChildren`), so
+the fix is exactly the shape this filing asked for: `UiScrollablePanel`
+now sets `ClipsChildren => true` and culls by INTERSECTION instead of
+full containment — straddling rows render their visible slice, clipped
+at the viewport edge for both drawing and clicks. Register row AP-201
+retired in the same commit. Pinned by
+`UiScrollablePanelTests.StraddlingRow_StaysVisible_AndClipsInsteadOfVanishing`
+and `ViewportClipsChildDrawingAndHitTesting`.
+
+<!-- original filing -->
+**(filed OPEN)** — 2026-08-11 at the OP5 review-fix round (S2).
 `UiScrollablePanel.LayoutScrollableChildren` (`src/AcDream.App/UI/UiScrollablePanel.cs:69`)
 has no scissor stack, so a row that straddles the viewport's visible edge is
 hidden WHOLE (`child.Visible = top >= -0.5f && top + child.Height <=