#15671: fix(feishu): Credentials check bug of Feishu bitable tools when using multiple accounts configuration

## Problem (A cleaner version of https://github.com/openclaw/openclaw/pull/15637) When using the multiple accounts configuration described in [the documentation](https://docs.openclaw.ai/channels/feishu#multiple-accounts), the appId and appSecret are defined in the nested under accounts.main. Meanwhile, the [registration function of the bitable tools](https://github.com/openclaw/openclaw/blob/45b9aad0f4384ce16f99885f86a5dd7488638c47/extensions/feishu/src/bitable.ts#L314) checks that both feishuCfg?.appId and feishuCfg?.appSecret exist, which won't under the multi-accounts configuration. This leads to the registration failure of the bitable tools described in extensions/feishu/src/bitable.ts, causing the agent to be unable to operate in any bitable in feishu. ## Fix This pr fixes this by adding support to both single- and multi-accounts. When using a single-account configuration, the config is directly passed to createFeishuClient. When one of appId and appSecret is not found, it switches to the multi-accounts configuration and filters accounts with appId and appSecret checks, then use the cfg of the first account with credential to create feishu client. ## Related Issues https://github.com/openclaw/openclaw/issues/15590 <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates Feishu bitable tool registration to support both single-account configs (top-level `appId`/`appSecret`) and multi-account configs (credentials nested under `channels.feishu.accounts.*`). It does so by selecting either the top-level Feishu config or the first enabled+configured account returned by `listEnabledFeishuAccounts`, then using that config to create the Feishu client used by the bitable tools. One issue to address before merge: in multi-account mode the chosen config omits `accountId`, which interacts poorly with `createFeishuClient`'s per-`accountId` cache and can lead to client cache collisions and wrong credentials being used. <h3>Confidence Score: 4/5</h3> - Mostly safe to merge, but fix the multi-account client cache collision first. - Changes are localized to Feishu bitable tool registration and correctly add multi-account credential discovery, but multi-account mode currently drops `accountId`, which can cause `createFeishuClient` to reuse/overwrite the cached client under the default cache key and lead to incorrect credentials being used. - extensions/feishu/src/bitable.ts _{Last reviewed commit: c8675c1} <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} <!-- /greptile_comment -->