feat: temp HP, character isNpc, initiative box

Temp HP:
- setTempHp() in shared/turn.js (replaces, no stacking)
- Damage absorbs temp HP first (both 5e + generic rulesets)
- Inline temp HP input on participant card (cyan when active)
- Temp HP field in edit modal
- makeParticipant tempHp field (default 0)
- 8 shared tests

Character isNpc:
- isNpc field on character roster model
- buildCharacterParticipant: type 'npc' when isNpc
- Add form checkbox + edit form checkbox
- NPC badge on character list row
- Writeback preserves isNpc

Initiative box:
- Amber-bordered box around initiative input
- Gold text (amber-300), disabled stays gold
- Stone-950 bg matches page
- Bumped maxHp (stone-200) + tempHp (stone-300/cyan) visibility

shared/tests/turn.temphp.test.js

@@ -0,0 +1,102 @@
+// Temp HP: damage hits temp first, then regular.
+// setTempHp replaces (no stacking). Healing regular HP ignores temp.
+const shared = require('@ttrpg/shared');
+const { makeParticipant, applyHpChange, setTempHp, addParticipant } = shared;
+const { mockCtx } = require('./_helpers');
+
+function setupEnc() {
+  const { ctx } = mockCtx();
+  return {
+    enc: { id: 'enc1', name: 'TempEnc', participants: [], isStarted: false, isPaused: false, round: 0 },
+    ctx,
+  };
+}
+
+describe('temp HP', () => {
+  test('setTempHp sets tempHp on participant', async () => {
+    const { enc, ctx } = setupEnc();
+    const p = makeParticipant({
+      name: 'Hero', type: 'character', initiative: 10, maxHp: 20, currentHp: 20,
+    });
+    let e = await addParticipant(enc, p, ctx);
+    e = await setTempHp(e, p.id, 5, ctx);
+    expect(e.participants[0].tempHp).toBe(5);
+  });
+
+  test('setTempHp replaces existing temp (no stacking)', async () => {
+    const { enc, ctx } = setupEnc();
+    const p = makeParticipant({
+      name: 'Hero', type: 'character', initiative: 10, maxHp: 20, currentHp: 20,
+    });
+    let e = await addParticipant(enc, p, ctx);
+    e = await setTempHp(e, p.id, 5, ctx);
+    e = await setTempHp(e, p.id, 3, ctx);
+    expect(e.participants[0].tempHp).toBe(3);
+  });
+
+  test('setTempHp to 0 clears temp', async () => {
+    const { enc, ctx } = setupEnc();
+    const p = makeParticipant({
+      name: 'Hero', type: 'character', initiative: 10, maxHp: 20, currentHp: 20,
+    });
+    let e = await addParticipant(enc, p, ctx);
+    e = await setTempHp(e, p.id, 5, ctx);
+    e = await setTempHp(e, p.id, 0, ctx);
+    expect(e.participants[0].tempHp).toBe(0);
+  });
+
+  test('damage: temp absorbs before regular HP', async () => {
+    const { enc, ctx } = setupEnc();
+    const p = makeParticipant({
+      name: 'Hero', type: 'character', initiative: 10, maxHp: 20, currentHp: 20,
+    });
+    let e = await addParticipant(enc, p, ctx);
+    e = await setTempHp(e, p.id, 5, ctx);
+    e = await applyHpChange(e, p.id, 'damage', 8, ctx);
+    expect(e.participants[0].tempHp).toBe(0);
+    expect(e.participants[0].currentHp).toBe(17);
+  });
+
+  test('damage less than temp: only temp reduced', async () => {
+    const { enc, ctx } = setupEnc();
+    const p = makeParticipant({
+      name: 'Hero', type: 'character', initiative: 10, maxHp: 20, currentHp: 20,
+    });
+    let e = await addParticipant(enc, p, ctx);
+    e = await setTempHp(e, p.id, 10, ctx);
+    e = await applyHpChange(e, p.id, 'damage', 4, ctx);
+    expect(e.participants[0].tempHp).toBe(6);
+    expect(e.participants[0].currentHp).toBe(20);
+  });
+
+  test('heal: does not affect temp HP', async () => {
+    const { enc, ctx } = setupEnc();
+    const p = makeParticipant({
+      name: 'Hero', type: 'character', initiative: 10, maxHp: 20, currentHp: 10,
+    });
+    let e = await addParticipant(enc, p, ctx);
+    e = await setTempHp(e, p.id, 5, ctx);
+    e = await applyHpChange(e, p.id, 'heal', 8, ctx);
+    expect(e.participants[0].tempHp).toBe(5);
+    expect(e.participants[0].currentHp).toBe(18);
+  });
+
+  test('damage exactly equals temp: temp gone, regular intact', async () => {
+    const { enc, ctx } = setupEnc();
+    const p = makeParticipant({
+      name: 'Hero', type: 'character', initiative: 10, maxHp: 20, currentHp: 20,
+    });
+    let e = await addParticipant(enc, p, ctx);
+    e = await setTempHp(e, p.id, 5, ctx);
+    e = await applyHpChange(e, p.id, 'damage', 5, ctx);
+    expect(e.participants[0].tempHp).toBe(0);
+    expect(e.participants[0].currentHp).toBe(20);
+  });
+
+  test('makeParticipant: tempHp defaults to 0', async () => {
+    const p = makeParticipant({
+      name: 'Hero', type: 'character', initiative: 10, maxHp: 20, currentHp: 20,
+    });
+    expect(p.tempHp).toBe(0);
+  });
+});