feat(discord-control): add channel-private-update and member-list field projection

docs/DISCORD_CONTROL.md

@@ -16,6 +16,7 @@ export AUTH_TOKEN='strong-token'
 # export REQUIRE_AUTH_TOKEN=true
 # optional action gates
 # export ENABLE_CHANNEL_PRIVATE_CREATE=true
+# export ENABLE_CHANNEL_PRIVATE_UPDATE=true
 # export ENABLE_MEMBER_LIST=true
 # optional allowlist
 # export ALLOWED_GUILD_IDS='123,456'
@@ -70,6 +71,33 @@ curl -sS http://127.0.0.1:8790/health
 
 ---
 
+## Action: channel-private-update
+
+对现有频道的白名单/覆盖权限做增删改。
+
+### Request
+
+```json
+{
+  "action": "channel-private-update",
+  "guildId": "123",
+  "channelId": "789",
+  "mode": "merge",
+  "addUserIds": ["111"],
+  "addRoleIds": ["333"],
+  "removeTargetIds": ["222"],
+  "allowMask": "67648",
+  "denyMask": "0",
+  "dryRun": false
+}
+```
+
+说明：
+- `mode=merge`：在现有覆盖基础上增删
+- `mode=replace`：重建覆盖（保留/补上 @everyone deny）
+
+---
+
 ## Action: member-list
 
 ### Request
@@ -79,13 +107,15 @@ curl -sS http://127.0.0.1:8790/health
   "action": "member-list",
   "guildId": "123",
   "limit": 100,
-  "after": "0"
+  "after": "0",
+  "fields": ["user.id", "user.username", "nick", "roles", "joined_at"]
 }
 ```
 
 说明：
 - `limit` 1~1000
 - `after` 用于分页（Discord snowflake）
+- `fields` 可选：字段裁剪，减小返回体；可用 `user.xxx` 选子字段
 
 ---