docs: Apply documentation standards across all docs (#49177)

## Summary

Comprehensive remediation of 146 documentation files to align with Zed's
documentation conventions and brand voice guidelines.

## Changes

### YAML Frontmatter
- Added `title` and `description` frontmatter to all docs missing it

### Settings UI Pattern
- Updated 48+ files to show Settings Editor before JSON examples
- Pattern: `Configure X in Settings ({#kb zed::OpenSettings}), or add to
your settings file:`
- Added `([how to edit](./configuring-zed.md#settings-files))` links for
JSON-only settings

### Brand Voice Fixes
- Removed exclamation points (command-palette, key-bindings, repl,
privacy-and-security, etc.)
- Simplified em dash chains to parentheticals (environment,
troubleshooting, agent-panel, etc.)
- Fixed marketing language (yarn.md intro, development/linux.md)

### Terminology Alignment
- `settings UI` -> `Settings Editor`
- `sidebar` -> specific panel names (Project Panel, Collab Panel)
- `directory` -> `folder` in non-technical contexts
- `workspace` -> `project` in non-LSP contexts
- `Command Palette` -> `command palette` (lowercase)

### Callout Standardization
- Converted various callout formats to standard `> **Note:**` pattern

## Related

Depends on conventions established in #49176.

Release Notes:

- N/A

docs/src/getting-started.md

@@ -5,9 +5,9 @@ description: Get started with Zed, the fast open-source code editor. Essential c
 
 # Getting Started
 
-Welcome to Zed! We are excited to have you. Zed is a powerful multiplayer code editor designed to stay out of your way and help you build what's next.
+Zed is an open-source code editor with built-in collaboration and AI tools.
 
-This guide gets you from zero to productive in Zed. You'll learn the essential commands, configure your environment, and find your way around.
+This guide covers the essential commands, environment setup, and navigation basics.
 
 ## Quick Start
 
@@ -77,7 +77,7 @@ You can also enable familiar keybindings:
 
 ## Join the Community
 
-Zed is proudly open source, and we get better with every contribution. Join us on GitHub or in Discord to contribute code, report bugs, or suggest features.
+Zed is open source. Join us on GitHub or in Discord to contribute code, report bugs, or suggest features.
 
 - [Discord](https://discord.com/invite/zedindustries)
 - [GitHub Discussions](https://github.com/zed-industries/zed/discussions)