## DESCRIBE YOUR PR

Closes #14106

Adds developer docs for our MCP Server instrumentation. 

Route for the documentation `sdk/expected-features/mcp-instrumentation`
that includes:

```bash
.mcp-instrumentation
├── index.mdx  # brief description on current features and limitations
├── errors.mdx # draft errors doc 
└── tracing.mdx # Tracing and span conventions
```

Followed this file structure as a start to (in the future) have this
structure for all the other features, having something like this below,
where we have :
```
.[Feature 1]
├── index.mdx 
├── logs.mdx 
├── errors.mdx 
.
.
.
.[Feature 2]
├── index.mdx 
├── errors.mdx 
├── tracing.mdx
.
.
.
 ```

The structure idea is from @abhi, who helped me settle this <3.

**NOTE:** Error docs are going to change, addressing feedback from [sentry-javascript/pull/16817](getsentry/sentry-javascript#16817)

## IS YOUR CHANGE URGENT?  


## PRE-MERGE CHECKLIST

*Make sure you've checked the following before merging your changes:*

- [x] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter experts)
- [ ] PR was reviewed and approved by a member of the [Sentry docs team](https://github.com/orgs/getsentry/teams/docs)

---------

Co-authored-by: Alex Krawiec <alex.krawiec@sentry.io>