feat: ritual + judgment + favor + cross-over (Workstream B)

Implements Workstream B of the character-depth-ghost-log spec:
ritual_start/ritual_step/judgment WS handlers, the pure judgment.py
logic module, and the User.favor / Entity.at_peace columns + migration.

- app/judgment.py: pure ritual success roll (base 65%, floored at 30%,
  driven by an entity's power+deceptiveness difficulty), the "stuck
  spirit" cross_over rule (alignment >= 0.5 and volatility > 0.6, ~20%
  of entities), judgment correctness/favor-delta/essence-delta/
  consequence resolution for all four verdicts, favor clamping, the
  favor-to-trait-roll bias applied at mint time, and tell-line
  generation (opaque behavioral flavor text, never a raw stat).
- app/ws.py: wires ritual_start/ritual_step/judgment frames, emits
  ritual_complete/tell/judgment_result/item_drop per the spec's
  Contract; traits are added to serialize_entity for internal
  server-side use but stripped from the outbound `entity` frame via a
  new _public_entity helper so hidden ground truth never reaches the
  client outside ritual_complete; _summon excludes at-peace entities
  from signature re-contact and mints a fresh (salted-signature) entity
  instead; new entities' traits are nudged by the discovering user's
  favor before being persisted.
- models/user.py, models/entity.py, main.py: User.favor and
  Entity.at_peace columns plus their idempotent ADD COLUMN IF NOT
  EXISTS migration lines in lifespan, alongside the existing ones.
- tests/test_judgment.py, tests/test_ws_ritual_judgment.py: 56 new
  tests covering the ritual/judgment correctness matrix, favor
  clamping/bias, essence crediting, at_peace persistence + re-contact,
  and the entity-frame trait leak guard.

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

backend/app/main.py

@@ -54,6 +54,13 @@ async def lifespan(app: FastAPI):
         await conn.execute(text(
             "ALTER TABLE entities ADD COLUMN IF NOT EXISTS traits JSONB NOT NULL DEFAULT '{}'::jsonb"
         ))
+        # Workstream B (character-depth-ghost-log spec).
+        await conn.execute(text(
+            "ALTER TABLE users ADD COLUMN IF NOT EXISTS favor DOUBLE PRECISION NOT NULL DEFAULT 0.0"
+        ))
+        await conn.execute(text(
+            "ALTER TABLE entities ADD COLUMN IF NOT EXISTS at_peace BOOLEAN NOT NULL DEFAULT false"
+        ))
     cleanup_task = asyncio.create_task(_session_cleanup_loop())
     try:
         yield