docs: agent builder cleanup (#1571)

## Overview
Previously, the tools page had a weird green in light mode:
<img width="1808" height="555" alt="Screenshot 2025-11-21 at 1 46 12 PM"
src="https://github.com/user-attachments/assets/336709c2-d0ba-4875-b267-9d05e911fc7c"
/>

Now it matches the other notes (and looks good in dark and light mode):
<img width="1613" height="452" alt="Screenshot 2025-11-21 at 1 46 40 PM"
src="https://github.com/user-attachments/assets/09f3b604-7f45-4681-b717-9b09fa404405"
/>

Also the product is now in Beta, not private preview. no more waitlist:
<img width="1347" height="373" alt="Screenshot 2025-11-21 at 1 47 22 PM"
src="https://github.com/user-attachments/assets/72298966-91ac-4802-8072-bbee2a86dca0"
/>



## Type of change

**Type:** [Replace with: New documentation page / Update existing
documentation / Fix typo/bug/link/formatting / Remove outdated content /
Other]

## Related issues/PRs
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## Checklist
<!-- Put an 'x' in all boxes that apply -->
- [ ] I have read the [contributing guidelines](README.md)
- [ ] I have tested my changes locally using `docs dev`
- [ ] All code examples have been tested and work correctly
- [ ] I have used **root relative** paths for internal links
- [ ] I have updated navigation in `src/docs.json` if needed

(Internal team members only / optional): Create a preview deployment as
necessary using the [Create Preview Branch
workflow](https://github.com/langchain-ai/docs/actions/workflows/create-preview-branch.yml)

## Additional notes
<!-- Any other information that would be helpful for reviewers -->

Author: joaquin-borggio-lc

src/langsmith/agent-builder-tools.mdx

@@ -6,9 +6,7 @@ mode: wide
 
 Use these built-in tools to give your agents access to email, calendars, chat, project management, search, social, and general web utilities.
 
-<Callout icon="circle-info" color="#DCFCE7" iconType="regular">
-  Google, Slack, Linear, and LinkedIn use OAuth. Exa, Tavily, and Twitter/X use workspace secrets.
-</Callout>
+<Note> Google, Slack, Linear, and LinkedIn use OAuth. Exa, Tavily, and Twitter/X use workspace secrets.</Note>
 
 <CardGroup cols={2}>
   <Card title="Gmail" icon="google">

src/langsmith/agent-builder.mdx

@@ -5,7 +5,7 @@ mode: wide
 ---
 
 <Callout icon="wand-magic-sparkles" color="#2563EB" iconType="regular">
-Agent Builder is in private preview. Sign up for the waitlist [today](https://www.langchain.com/langsmith-agent-builder-waitlist).
+Agent Builder is in Beta.
 </Callout>
 
 Agent Builder lets you turn natural-language ideas into production agents. It's powered by [deep-agents](https://github.com/langchain-ai/deepagents), and is not <Tooltip tip="Predetermined code paths that are designed to operate in a certain order.">workflow based</Tooltip>.