feat(hermes): add context engine controls

tests/hermes-config-page-ui.test.js

@@ -150,6 +150,15 @@ test('Hermes 配置页会暴露 X 搜索结构化配置字段', () => {
   }
 })
 
+test('Hermes 配置页会暴露上下文引擎结构化配置字段', () => {
+  for (const id of [
+    'hm-context-config-save',
+    'hm-context-engine',
+  ]) {
+    assert.match(source, new RegExp(`id="${id}"`), `缺少 ${id}`)
+  }
+})
+
 test('Hermes 配置页会暴露 provider 超时覆盖结构化配置字段', () => {
   for (const id of [
     'hm-provider-overrides-save',

tests/hermes-context-config.test.js

@@ -0,0 +1,58 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+
+import {
+  buildHermesContextConfigValues,
+  mergeHermesContextConfig,
+} from '../scripts/dev-api.js'
+
+test('Hermes 上下文引擎配置读取会提供上游默认值', () => {
+  const values = buildHermesContextConfigValues({})
+
+  assert.deepEqual(values, {
+    contextEngine: 'compressor',
+  })
+})
+
+test('Hermes 上下文引擎配置读取会回显 YAML 字段', () => {
+  const values = buildHermesContextConfigValues({
+    context: {
+      engine: 'lcm',
+    },
+  })
+
+  assert.equal(values.contextEngine, 'lcm')
+})
+
+test('Hermes 上下文引擎配置保存会保留未知字段并写入上游结构', () => {
+  const next = mergeHermesContextConfig({
+    context: {
+      engine: 'compressor',
+      custom_flag: 'keep-context',
+    },
+    model: { provider: 'anthropic' },
+    streaming: { enabled: true },
+  }, {
+    contextEngine: 'lcm',
+  })
+
+  assert.deepEqual(next.model, { provider: 'anthropic' })
+  assert.deepEqual(next.streaming, { enabled: true })
+  assert.equal(next.context.engine, 'lcm')
+  assert.equal(next.context.custom_flag, 'keep-context')
+})
+
+test('Hermes 上下文引擎配置保存会拒绝非法引擎名', () => {
+  assert.throws(
+    () => mergeHermesContextConfig({}, { contextEngine: '' }),
+    /context\.engine/,
+  )
+  assert.throws(
+    () => mergeHermesContextConfig({}, { contextEngine: 'bad engine' }),
+    /context\.engine/,
+  )
+  assert.throws(
+    () => mergeHermesContextConfig({}, { contextEngine: '中文' }),
+    /context\.engine/,
+  )
+})