fix #381: Options-panel footer needs an opaque backing field

Root cause: a live-DAT probe found retail authors NO backing element
behind the Character/Chat/Config tabs' Apply/Reset/Defaults footer —
each page root has exactly five children (the row ListBox, its
scrollbar, and the three buttons) with zero direct-state media on the
root itself. Scrolled row content therefore bled through visibly
between/behind the three buttons; the bleed-through is a rendering gap
in our own composition, not a missing import.

Fix: new minimal widget UiSolidSpriteFill tiles
RetailChromeSprites.CenterFill (the SAME panel-background sprite the
Options window's own chrome already draws behind everything, not an
invented color) across the footer strip's rect, derived from the three
buttons' own resolved Top/Height and z-ordered strictly behind every
other child so it can never intercept input or occlude the buttons.
Register row AP-205 records the synthesis. Regressed by
OptionsPanelControllerTests.
Bind_SynthesizesOneOpaqueFooterBacking_PerPageWithApplyResetDefaults,
which pins exactly one backing field per page, sized from the live
button rects, z-ordered behind every sibling.

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

docs/ISSUES.md

@@ -38,16 +38,35 @@ button starts in, what media that state resolves) — before fixing.
 
 ## #381 — Options-panel footer (Apply/Reset/Defaults) needs an opaque backing field; list content shows through between the buttons
 
-**Status:** OPEN — filed 2026-08-11 at Campaign OP gate 4 (user report).
-The Apply/Reset/Defaults row draws its three buttons directly over the
-page content, so scrolled rows/text remain visible between and behind
-them. Retail's tabs give that footer strip its own solid rectangular
-field (no border) that occludes the content underneath. Fix: an opaque
-borderless backing panel behind the footer button row on every page that
-has the three buttons (Character/Chat/Config, and the equivalent strip on
-Configure Keyboard if its authored layout shows the same bleed-through).
-Check first whether the authored LayoutDescs carry such a field element
-we fail to draw (preferred: draw the authored one) before synthesizing.
+**Status:** ROOT-CAUSED + FIXED (this commit) — pending the user's
+re-gate. Filed 2026-08-11 at Campaign OP gate 4 (user report).
+
+**ROOT CAUSE — confirmed a genuine acdream synthesis, retail authors no
+backing element either.** A live-DAT probe dumped the Character/Chat/
+Config page roots' (`0x100001F9`/`0x100001FF`/`0x1000050A`) full
+top-level child inventory: each has EXACTLY five children — the row
+ListBox, its scrollbar, and the three physical buttons — with ZERO
+direct-state media on the page root itself. Retail's own footer strip has
+no authored backdrop; the bleed-through was a rendering gap, not a
+missing import. **Fix:** a new minimal widget, `UiSolidSpriteFill`, tiles
+`RetailChromeSprites.CenterFill` (the SAME panel-background sprite the
+Options window's own chrome already draws behind everything, not an
+invented color) across the footer strip's rect (derived from the three
+buttons' own resolved Top/Height, spanning the full page width),
+z-ordered strictly behind every other child so it can never occlude the
+buttons. Register row AP-205 records the synthesis (Configure Keyboard
+was NOT touched — its own footer strip was not probed and is out of this
+fix's scope; file a follow-up if it shows the same bleed-through).
+Regressed by
+`tests/AcDream.App.Tests/UI/Layout/OptionsPanelControllerTests.cs`
+(`Bind_SynthesizesOneOpaqueFooterBacking_PerPageWithApplyResetDefaults`
+— pins exactly one backing field per page, sized from the live button
+rects, z-ordered behind every sibling).
+
+**Re-gate (§OP4/OP5/OP6, "the list does not clip/overlap the Apply/
+Reset/Defaults buttons" steps): scrolled content should no longer be
+visible through or around the three footer buttons on any of the three
+tabs.**
 
 ## #380 — Chat tab: the two opacity sliders are missing their retail row captions
 

docs/research/2026-08-11-campaign-op-test-script.md

@@ -205,7 +205,12 @@ TrySetOption` seam every other Options-panel consumer already uses.
    FAILURE shape, not a crash, but still worth flagging which row).
 2. **Scroll the list** via the scrollbar. All 50+6 rows are reachable;
    the list does not clip or overlap the Apply/Reset/Defaults buttons at
-   the bottom.
+   the bottom. **Gate-4 re-test note (#381):** the footer strip behind the
+   three buttons previously had NO backing — scrolled row text/content was
+   visible bleeding through between and behind Apply/Reset/Defaults. The
+   footer now has an opaque backing field; report if any content is still
+   visible through or around the three buttons (this applies identically
+   on the Chat and Config tabs' own footer strips, OP5/OP6 below).
 3. **Confirm the checkboxes reflect your character's actual state** —
    e.g. if you have `IgnoreAllegianceRequests` on from a prior session,
    its row should show checked on open (seeded from the live server bit
@@ -411,7 +416,9 @@ chat windows already read when deciding which lines to show.
    cleanly at the panel's bottom edge — scrolling reveals the rest
    smoothly. A block that disappears ENTIRELY while its header stays (the
    pre-fix void your gate-3 screenshot review caught) is a regression —
-   report it.
+   report it. **Gate-4 re-test note (#381):** see the Character-tab (OP4)
+   step 2 note — the SAME opaque-footer-backing fix applies to this tab's
+   own Apply/Reset/Defaults strip.
 3. **Look closely at a row whose mask covers MULTIPLE underlying message
    types** (Gameplay, Combat, Allegiance, or Fellowship — the composite-mask
    rows per the research doc) versus a single-bit row (e.g. "Error" or
@@ -590,7 +597,8 @@ should show no caption.
    invented English when a string fails to resolve).
 2. **Scroll the list** via the scrollbar. All 27 rows are reachable; the
    list does not clip or overlap the Apply/Reset/Defaults buttons at the
-   bottom.
+   bottom. **Gate-4 re-test note (#381):** see the Character-tab (OP4)
+   step 2 note above — the SAME opaque-footer-backing fix applies here.
 
 ### Live rows — audio