V2 Phase 2: spell + resource enforcement (sheet → combat → live)

The Slice-0 vertical that proves the enforcement architecture end-to-end.

- kernel: castSpell (slot consumption + concentration set/replace, upcasting,
  warlock pact slots), spendResource/regainResource, rollDeathSave — pure
  functions returning Partial<Character> patches. 13 unit tests.
- applyRest now ends concentration on any rest (+ test).
- character sheet SpellcastingSection: per-spell Cast button, concentration
  banner with Drop, concentration markers; ResourcesSection −/+ routed through
  the kernel.
- player MyCharacterPanel: castable spell list + concentration banner, so a
  seated player casts and it broadcasts via the existing playerPatch flow.
- live sync: partialCharacterDiffSchema carries concentration; GM applies it;
  playerCharacterSchema mirrors slots/concentration/resources (PC-only) and the
  player-facing AC now respects equippedArmor. Wire round-trip test added.

Verified live: casting decrements the right slot, switching concentration logs
"Concentration on X ends", banner + Drop render. Build + 258 tests green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/rules/depth.test.ts

@@ -98,4 +98,12 @@ describe('applyRest', () => {
     expect(patch.defenses!.exhaustion).toBe(1);
     expect(patch.defenses!.deathSaves).toEqual({ successes: 0, failures: 0 });
   });
+
+  it('any rest ends ongoing concentration', () => {
+    const c = { ...makeCharacter(), concentration: { spellId: 's', spellName: 'Bless' } };
+    const short = dnd5e.restOptions.find((o) => o.id === 'short')!;
+    expect(applyRest(c, short).concentration).toBeNull();
+    // no concentration → no concentration key in the patch
+    expect('concentration' in applyRest(makeCharacter(), short)).toBe(false);
+  });
 });