docs: Apply brand voice standards to AI documentation (#48401)

## Summary

Reviewed and updated all 18 files in `docs/src/ai/` to meet Zed's brand
voice standards. Each file was scored against the 8-criterion rubric and
rewritten where needed to achieve 4+ on all criteria.

**Changes include:**
- Remove "Learn how to/about" patterns (8 instances)
- Replace vague phrases ("various types of tasks", "and more") with
specific examples
- Remove taboo words ("seamless", "naturally extends")
- Remove emotional language ("We're excited/thrilled/happy")
- Remove marketing patterns ("Stay tuned!", exclamation points)
- Remove unverifiable claims ("world's fastest")
- Replace hedging with direct statements
- Remove promotional emphasis (`_free_`, `**_for free_**`)
- Fix typo in external-agents.md ("servers" → "serves")
- Fix broken link syntax for Ollama Turbo

## Test plan

- [x] `mdbook build` succeeds
- [x] Grep for remaining taboo phrases (only one "seamless" in MCP
official quote, preserved intentionally)
- [x] All facts preserved (URLs, keybindings, settings keys, prices,
model names)

Fixes AI-8

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

docs/src/remote-development.md

@@ -1,6 +1,6 @@
 # Remote Development
 
-Remote Development allows you to code at the speed of thought, even when your codebase is not on your local machine. You use Zed locally so the UI is immediately responsive, but offload heavy computation to the development server so that you can work effectively.
+Remote Development lets you edit code on a remote server while running Zed locally. The UI stays responsive because it runs on your machine, while language servers, tasks, and terminals run on the server.
 
 ## Overview