feat(web): 角色群像按定位配比生成（role_mix 缩减版）

- 契约: CharacterGenerateRequest 加 role_mix{定位:数量}，model_validator 归一
  count=各值之和（每项≥1、总和≤12），缺省退回单一 role+count
- @llm: build_character_gen_context/run_character_gen 加 role_mix 参并注入配比块
  （确定性、无时间戳，守 assemble 纯函数）；router 穿参
- character-gen.md 加"按配比严格分配 role"纪律 + regen prompt_hashes 金标准
- 前端: sanitizeRoleMix/roleMixTotal + buildCharacterGenerateRequest 第4参 +
  useCharacterGen 穿参 + RoleMixEditor + CharacterGenerator 单一/配比双模

packages/core/tests/test_generation_node.py

@@ -181,6 +181,39 @@ def test_build_character_gen_context_injects_existing_and_generated() -> None:
     assert "苏黎" in ctx  # 本批已生成卡
 
 
+def test_build_character_gen_context_injects_role_mix() -> None:
+    # ⑦ 群像按定位配比：role_mix 各定位 + 数量都进上下文，指示模型按配比分配
+    ctx = build_character_gen_context(
+        brief="给我一组群像",
+        count=6,
+        role=None,
+        world_context="",
+        existing_chars=[],
+        generated_so_far=[],
+        role_mix={"主角": 1, "对手": 2, "配角": 3},
+    )
+
+    assert "配比" in ctx  # 配比块标识
+    assert "主角" in ctx and "对手" in ctx and "配角" in ctx
+    assert "1" in ctx and "2" in ctx and "3" in ctx
+
+
+def test_build_character_gen_context_role_mix_overrides_single_role() -> None:
+    # role_mix 在场时用配比块，不再输出单一「角色定位：role」行
+    ctx = build_character_gen_context(
+        brief="群像",
+        count=3,
+        role="主角",  # 应被 role_mix 覆盖
+        world_context="",
+        existing_chars=[],
+        generated_so_far=[],
+        role_mix={"对手": 3},
+    )
+
+    assert "角色定位：主角" not in ctx
+    assert "对手" in ctx
+
+
 def test_build_character_gen_context_handles_empty_anti_dup() -> None:
     # 首次单生成：无已有/已生成时仍产出可用上下文（不崩）
     ctx = build_character_gen_context(
@@ -243,6 +276,29 @@ async def test_run_character_gen_injects_anti_dup_into_request() -> None:
     assert "九转炼气" in req.input  # 世界观约束注入
 
 
+async def test_run_character_gen_injects_role_mix_into_request() -> None:
+    # ⑦ role_mix 穿参：run → build_character_gen_context → 请求 input 含各定位
+    gateway = FakeRunGateway(_CARDS)
+
+    await run_character_gen(
+        character_gen_spec,
+        brief="群像",
+        count=5,
+        role=None,
+        world_context="",
+        existing_chars=[],
+        generated_so_far=[],
+        gateway=gateway,
+        user_id=USER,
+        project_id=PROJECT,
+        role_mix={"主角": 2, "配角": 3},
+    )
+
+    req = gateway.last_request
+    assert req is not None
+    assert "配角" in req.input  # 配比定位注入
+
+
 async def test_run_character_gen_raises_when_gateway_fails() -> None:
     gateway = FailingRunGateway(RuntimeError("provider down"))