fix: group chat UX polish and model switch cleanup (#205)

* fix(chat): clamp context remaining tokens to 0 instead of showing negative

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: group chat mention popup position, timestamp style, and model switch cleanup

- Move @ mention popup above input to avoid blocking the textarea
- Fix .msg-time scoping (was nested inside .msg-header, now top-level)
- Reduce timestamp opacity and set to 12px for subtler display
- Clean up stale base_url/api_key from config.yaml on model switch

Closes #204

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: remove unused variables in GroupChatInput

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/server/src/controllers/hermes/models.ts

@@ -139,6 +139,8 @@ export async function setConfigModel(ctx: any) {
     const config = await readConfigYaml()
     if (typeof config.model !== 'object' || config.model === null) { config.model = {} }
     config.model.default = defaultModel
+    delete config.model.base_url
+    delete config.model.api_key
     if (reqProvider) { config.model.provider = reqProvider }
     await writeConfigYaml(config)
     ctx.body = { success: true }