fix #380: Chat tab opacity sliders were missing their retail row captions

Root cause: PlayerOptionPage::AddSliderOption never sets a row's own
name-label text — the "Inactive Opacity"/"Active Opacity" caption comes
from a SEPARATE DAT-resident runtime catalog (DID 0x78000000, resolved
via the same two-level DBCache::GetDIDFromEnumStatic master-map/submap
lookup ChatOptionsDatDefaults already uses for enum 0x16/category 2,
here for enum 0x15/category 2) that nothing in the codebase ever
queried, so both slider rows rendered with no caption at all.

Fix: new ChatOptionsDatCaptions.TryRead resolves the DID-0x78000000
catalog's per-property name/tooltip entries (matched by the same
owning-property enum ChatOptionsDatDefaults already keys its defaults
by) and ChatOptionsPageController.BuildOpacitySliders stamps each
slider's own row caption/tooltip from it — falling back to no text
(never invented English) if resolution fails. Regressed by
ChatOptionsPageControllerTests.
Bind_WiresEachSlidersOwnRowCaption_FromTheResolvedDatCatalog and the
companion Bind_MissingCaption_RendersNoText_NeverInventsEnglish case,
plus a live-mount probe (OptionsPanelLiveMountProbeTests.
ProbeChatOpacityCaptions) confirming the production TryRead call
resolves "Inactive Opacity"/"Active Opacity" against the real DAT.

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

src/AcDream.App/UI/Layout/ChatOptionsDatCaptions.cs

@@ -0,0 +1,129 @@
+using AcDream.Content;
+using DatReaderWriter.DBObjs;
+using DatReaderWriter.Types;
+
+namespace AcDream.App.UI.Layout;
+
+/// <summary>
+/// #380 (Campaign OP gate 4, 2026-08-11): reads the Chat tab's two opacity-slider
+/// row CAPTIONS ("Inactive Opacity" / "Active Opacity") + tooltips from the
+/// installed DAT — retail <c>UIOption::InqGameplayOptionNameAndTooltip
+/// @0x004ef750</c>'s own catalog lookup, the mechanism
+/// <c>UIOption_Slider::SetGameplayOptionProperty @0x00485030</c> calls for
+/// EVERY <c>UIOption_Slider</c> (both Chat opacity rows go through this path —
+/// see <c>gmChatOptionsUI::InitOptions</c>'s own <c>SetGameplayOptionProperty</c>
+/// calls at <c>0x0049fcc0</c>/<c>0x0049fd1a</c>). <c>PlayerOptionPage::AddSliderOption</c>
+/// itself never sets a row caption (byte-verified — no <c>StringInfo</c> write in
+/// its pseudo-C body), so the row's name-label child (element <c>0x1000021B</c>,
+/// shared by BOTH the unlabelled and range-captioned slider templates) is never
+/// populated by <c>AddSliderOption</c>, nor is it baked statically into the
+/// LayoutDesc (the SAME shared template element is reused for every slider on
+/// every tab, so it cannot carry a fixed caption) — <see cref="ChatOptionsPageController"/>
+/// never wired ANY source for it, which is #380's root cause.
+///
+/// <para>
+/// <b>Byte-verified recipe</b> (a SECOND <c>DBCache::GetDIDFromEnumStatic</c>
+/// sub-map lookup, sibling to <see cref="ChatOptionsDatDefaults"/>'s own
+/// <c>(0x16, 2)</c> defaults catalog): <c>InqGameplayOptionNameAndTooltip</c>'s own
+/// call site is <c>GetDIDFromEnumStatic(&amp;ret, 0x15, 2)</c> — SAME master-map
+/// key (<c>2</c>) as the defaults lookup, DIFFERENT sub-map key (<c>0x15</c> vs
+/// <c>0x16</c>) — so <see cref="RetailDataIdResolver.Resolve"/>'s own
+/// <c>(enumValue, enumCategory)</c> order is <c>(0x15, 2)</c>. Empirically
+/// confirmed against the installed DATs: resolves to DID <c>0x78000000</c> (a
+/// DIFFERENT object than the defaults catalog's <c>0x78000001</c> — the two
+/// enum values genuinely name separate DAT objects, not two views of one). That
+/// DBProperties has ONE top-level entry, property <c>0xD2</c>, an
+/// <c>ArrayBaseProperty</c> of <c>StructBaseProperty</c> entries — one per
+/// registered <c>GameplayOptionProperty</c> in the whole game (not opacity-
+/// specific). Each entry carries: <c>0xD4</c> = name <c>StringInfo</c>,
+/// <c>0xD5</c> = tooltip <c>StringInfo</c>, <c>0xD6</c> = the
+/// <c>GameplayOptionProperty</c> id this entry describes (an
+/// <c>EnumBaseProperty</c>), <c>0xD7</c>/<c>0xD8</c> = unrelated floats. The
+/// live array has exactly two entries, matching
+/// <see cref="ChatOptionsDatDefaults.DefaultOpacityPropertyId"/> (<c>0xD6</c>
+/// = <c>0x10000080</c>) and <c>ActiveOpacityPropertyId</c> (<c>0xD6</c> =
+/// <c>0x10000081</c>) — resolving via table <c>0x2300000D</c> (the SAME
+/// TextFilter-family table #372 already established as this campaign's
+/// runtime-string home, not the compiled-symbol table <c>0x23000003</c> the
+/// section headers use) to <b>"Inactive Opacity"</b> /
+/// <b>"Active Opacity"</b> — exactly the two labels the user's gate-4 report
+/// named ("I also miss the text next to the bars for Inactive and Active
+/// Opacity").
+/// </para>
+/// </summary>
+public static class ChatOptionsDatCaptions
+{
+    /// <summary>DAT enum-category key for the FIRST (master-map) lookup — see
+    /// the class doc's byte-verified recipe (shared with
+    /// <see cref="ChatOptionsDatDefaults"/>'s own defaults lookup).</summary>
+    private const uint EnumCategory = 2u;
+
+    /// <summary>DAT enum-value key for the SECOND (sub-map) lookup — the
+    /// name/tooltip catalog, NOT <see cref="ChatOptionsDatDefaults"/>'s
+    /// <c>0x16</c> defaults catalog.</summary>
+    private const uint EnumValue = 0x15u;
+
+    private const uint CatalogArrayPropertyId = 0xD2u;
+    private const uint EntryNamePropertyId = 0xD4u;
+    private const uint EntryTooltipPropertyId = 0xD5u;
+    private const uint EntryOwningPropertyId = 0xD6u;
+
+    /// <summary>One resolved name/tooltip pair. Either half may be
+    /// <see langword="null"/> if its own <c>StringInfo</c> failed to resolve —
+    /// the caller renders no text rather than inventing English (matching
+    /// this codebase's uniform degrade discipline).</summary>
+    public readonly record struct Caption(string? Name, string? Tooltip);
+
+    /// <summary>
+    /// Resolves the Default/Active opacity sliders' row captions + tooltips
+    /// from the live DAT. Returns <see langword="false"/> only when the
+    /// catalog DID itself does not resolve or is not a <c>DBProperties</c> —
+    /// a missing INDIVIDUAL entry still returns <see langword="true"/> with
+    /// that pair's <see cref="Caption"/> left at its default (both null).
+    /// </summary>
+    public static bool TryRead(
+        IDatReaderWriter dats,
+        DatStringResolver strings,
+        out Caption defaultOpacity,
+        out Caption activeOpacity)
+    {
+        defaultOpacity = default;
+        activeOpacity = default;
+
+        uint did = RetailDataIdResolver.Resolve(dats, EnumValue, EnumCategory);
+        if (did == 0u || !dats.Portal.TryGet<DBProperties>(did, out DBProperties? props) || props is null)
+            return false;
+
+        if (!props.Properties.TryGetValue(CatalogArrayPropertyId, out BaseProperty? arrayProp)
+            || arrayProp is not ArrayBaseProperty array)
+            return false;
+
+        foreach (BaseProperty entry in array.Value)
+        {
+            if (entry is not StructBaseProperty entryStruct) continue;
+            if (!entryStruct.Value.TryGetValue(EntryOwningPropertyId, out BaseProperty? owningProp)
+                || owningProp is not EnumBaseProperty owningEnum)
+                continue;
+
+            if (owningEnum.Value == ChatOptionsDatDefaults.DefaultOpacityPropertyId)
+                defaultOpacity = ReadCaption(entryStruct, strings);
+            else if (owningEnum.Value == ChatOptionsDatDefaults.ActiveOpacityPropertyId)
+                activeOpacity = ReadCaption(entryStruct, strings);
+        }
+
+        return true;
+    }
+
+    private static Caption ReadCaption(StructBaseProperty entry, DatStringResolver strings)
+    {
+        string? name = entry.Value.TryGetValue(EntryNamePropertyId, out BaseProperty? nameProp)
+            && nameProp is StringInfoBaseProperty nameInfo
+                ? strings.Resolve(nameInfo.Value.TableId.DataId, nameInfo.Value.StringId, nameInfo.Value.Token)
+                : null;
+        string? tooltip = entry.Value.TryGetValue(EntryTooltipPropertyId, out BaseProperty? tooltipProp)
+            && tooltipProp is StringInfoBaseProperty tooltipInfo
+                ? strings.Resolve(tooltipInfo.Value.TableId.DataId, tooltipInfo.Value.StringId, tooltipInfo.Value.Token)
+                : null;
+        return new Caption(name, tooltip);
+    }
+}