Implement the 020-fix-zero-hp-opacity feature that replaces container-level opacity dimming with element-level opacity on individual leaf elements so that HP popover and condition picker render at full opacity for unconscious combatants

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

specs/020-fix-zero-hp-opacity/quickstart.md

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+# Quickstart: Fix Zero-HP Opacity
+
+**Feature**: 020-fix-zero-hp-opacity
+**Date**: 2026-03-06
+
+## Problem
+
+When a combatant reaches 0 HP, the entire row gets `opacity-50` applied to the outermost container. This cascades to absolutely-positioned child elements (HP adjust popover and condition picker dropdown), making them semi-transparent and hard to use.
+
+## Fix Location
+
+**Single file**: `apps/web/src/components/combatant-row.tsx`
+
+## Fix Strategy
+
+1. Remove `opacity-50` from the outer row `<div>` (line 312).
+2. Apply `opacity-50` to individual leaf/display elements within the row when `status === "unconscious"`:
+   - Initiative input
+   - Name display
+   - AC display
+   - HP current value button (inside `ClickableHp`)
+   - HP separator slash
+   - Max HP display
+   - Concentration button
+   - Condition tags
+   - Remove button
+3. The `HpAdjustPopover` and `ConditionPicker` components — which are absolutely positioned overlays — are **not** wrapped in any dimmed container, so they render at full opacity.
+
+## Key Constraint
+
+CSS `opacity` on a parent element creates a stacking context that affects all children. There is no way to "undo" a parent's opacity on a child element. The fix must ensure popovers are never DOM descendants of an element with reduced opacity.
+
+## Verification
+
+```bash
+pnpm --filter web dev   # Start dev server
+# 1. Add a combatant, set max HP, reduce current HP to 0
+# 2. Click HP value — popover should appear at full opacity
+# 3. Click conditions area — picker should appear at full opacity
+# 4. Row content (name, initiative, etc.) should still appear dimmed
+```
+
+## Quality Gate
+
+```bash
+pnpm check   # Must pass before commit
+```