Implement the 011-quick-hp-input feature that adds an inline damage/heal numeric input per combatant row with mode toggle, keyboard workflow, and visual distinction

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

specs/011-quick-hp-input/quickstart.md

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+# Quickstart: Quick HP Input
+
+## What this feature does
+
+Adds an inline damage/heal numeric input to each combatant row. Instead of editing the absolute HP value, the game master types a number (e.g., "7") and the system applies it as damage (subtract) or healing (add) to the combatant's current HP.
+
+## Key files to modify
+
+1. **`apps/web/src/components/quick-hp-input.tsx`** (NEW) -- The main component: numeric input + damage/heal mode toggle.
+2. **`apps/web/src/components/combatant-row.tsx`** (MODIFY) -- Integrate `QuickHpInput` into the combatant row layout alongside existing HP display.
+
+## Key files to understand (read-only)
+
+- `packages/domain/src/adjust-hp.ts` -- Domain function that applies signed deltas (negative = damage, positive = heal)
+- `packages/domain/src/types.ts` -- `Combatant` type with optional `maxHp`/`currentHp`
+- `apps/web/src/hooks/use-encounter.ts` -- `adjustHp(id, delta)` hook already exposed
+- `apps/web/src/components/ui/input.tsx` -- Base input component for consistent styling
+- `apps/web/src/components/ui/button.tsx` -- Base button component for toggle
+
+## How the pieces connect
+
+```
+QuickHpInput (new component)
+  |-- User types "7" in damage mode, presses Enter
+  |-- Calls onAdjustHp(combatantId, -7)
+  |
+CombatantRow
+  |-- Passes onAdjustHp prop to QuickHpInput
+  |
+useEncounter hook
+  |-- adjustHp(id, delta) -> adjustHpUseCase -> domain adjustHp()
+  |-- Domain clamps result to [0, maxHp]
+  |-- State updates, localStorage persists
+```
+
+## Running the feature locally
+
+```bash
+pnpm --filter web dev    # Start Vite dev server at localhost:5173
+```
+
+## Running tests
+
+```bash
+pnpm check               # Full quality gate (format + lint + typecheck + test)
+pnpm test                # All tests
+```
+
+No new domain tests needed -- `adjustHp` is already fully tested. New tests (if any) would be component-level tests for `QuickHpInput` keyboard behavior and mode toggling.