docs: add Assistant.md custom instructions for the docs assistant

[lynglaxco-cc]

Description

Adds a .mintlify/Assistant.md file to give the Mintlify docs assistant custom instructions.

Assistant.md is a Mintlify convention — the file's contents are added to the assistant's system prompt and used as system-level context for every response. They supplement rather than replace Mintlify's default instructions. There is no corresponding setting in docs.json and nothing to enable in the dashboard; the file's presence is the configuration.

Reference: https://www.mintlify.com/docs/assistant/customize

The file is placed in .mintlify/ rather than the project root because Mintlify serves a root-level Assistant.md publicly at /assistant.md. The .mintlify/ directory is not served publicly.

What the instructions cover:

1. Scope — the assistant answers from published documentation and has no access to any user's account, app, or dashboard.
2. No soliciting credentials — the assistant must not ask users for API keys, Auth Keys, auth tokens, or third-party provider credentials while troubleshooting. It asks for SDK version, platform, method, and error message instead. This is the main behavioral change.
3. Handling pasted credentials — if a user shares one anyway, the assistant does not echo the value, identifies the credential type, advises rotation, then answers the question. App ID and region are explicitly excluded, since they are client-side and not secrets.
4. Handling personal details — the assistant does not repeat back names, emails, phone numbers, or end-user data, and points account-specific questions to support.
5. Code examples — generated snippets use YOUR_API_KEY / <APP_ID> placeholders and the documented superhero1–superhero5 sample users.
6. Self-description — a short, accurate answer for users who ask what the assistant does with their input.

Why: the assistant currently has no instruction against requesting credentials during troubleshooting. Prompting a developer to paste an Auth Key into a chat box is a bad outcome regardless of what happens downstream, and it is cheap to prevent at the instruction layer.

Related Issue(s)

N/A

Type of Change

• Other — assistant configuration, not documentation content

Checklist

• I have read the CONTRIBUTING document
• My branch name follows the naming convention
• My changes follow the documentation style guide
• I have checked for spelling and grammar errors
• All links in my changes are valid and working
• My changes are accurately described in this pull request

Additional Information

No user-visible page is added. The file sits in .mintlify/, which Mintlify does not serve publicly, and is not referenced in navigation in docs.json. Nothing about the site's appearance changes.

Verify after deploy: request https://www.cometchat.com/docs/assistant.md and confirm it does not return the file.

Scope of effect: these instructions shape the assistant's responses. They do not filter, block, or alter what a user submits.

Rollback: delete the file — Mintlify's documented removal path for custom instructions.

Not tested in local preview — I don't have Mintlify dashboard access, so I couldn't run mint dev to verify assistant behavior. Requesting a reviewer with dashboard access to confirm before merge, particularly that ordinary questions mentioning App ID and region don't trigger an unnecessary warning.

Screenshots

N/A — no visual changes.