docs(plugin-sdk): refresh seam cleanup docs

docs/plugins/architecture.md

@@ -196,6 +196,12 @@ We do not publish separate `plugin-sdk/*-action-runtime` subpaths, and bundled
 plugins should import their own local runtime code directly from their
 extension-owned modules.
 
+The same boundary applies to provider-named SDK seams in general: core should
+not import `openclaw/plugin-sdk/slack`, `.../discord`, `.../signal`,
+`.../whatsapp`, or other channel-specific convenience barrels. If core needs a
+behavior, either consume the bundled plugin's own `api.ts` / `runtime-api.ts`
+barrel or promote the need into a narrow generic capability in the shared SDK.
+
 For polls specifically, there are two execution paths:
 
 - `outbound.sendPoll` is the shared baseline for channels that fit the common

docs/plugins/sdk-migration.md

@@ -46,6 +46,14 @@ The old approach caused problems:
 The modern plugin SDK fixes this: each import path (`openclaw/plugin-sdk/\<subpath\>`)
 is a small, self-contained module with a clear purpose and documented contract.
 
+Legacy provider convenience seams for bundled channels are also gone. Imports
+such as `openclaw/plugin-sdk/slack`, `openclaw/plugin-sdk/discord`,
+`openclaw/plugin-sdk/signal`, `openclaw/plugin-sdk/whatsapp`, and
+`openclaw/plugin-sdk/telegram-core` were private mono-repo shortcuts, not
+stable plugin contracts. Use narrow generic SDK subpaths instead. Inside the
+bundled plugin workspace, keep provider-owned helpers in that plugin's own
+`api.ts` or `runtime-api.ts`.
+
 ## How to migrate
 
 <Steps>

docs/plugins/sdk-overview.md

@@ -32,6 +32,13 @@ import { defineChannelPluginEntry } from "openclaw/plugin-sdk/core";
 Each subpath is a small, self-contained module. This keeps startup fast and
 prevents circular dependency issues.
 
+Do not add or depend on provider-named convenience seams such as
+`openclaw/plugin-sdk/slack`, `openclaw/plugin-sdk/discord`,
+`openclaw/plugin-sdk/signal`, or `openclaw/plugin-sdk/whatsapp`. Bundled plugins should compose generic SDK
+subpaths inside their own `api.ts` or `runtime-api.ts` barrels, and core should
+either use those plugin-local barrels or add a narrow generic SDK contract when
+the need is truly cross-channel.
+
 ## Subpath reference
 
 The most commonly used subpaths, grouped by purpose. The full list of 100+