docs: add Voice & Style guide and rewrite docs pages to match

Add a Voice & Style section to the docs authoring guide, then bring every
docs page in line with it: lead with the task, add success signals to
procedures, explain jargon on first use, keep bullet casing consistent,
and link out to Troubleshooting where steps can fail.

Applied across English source and all localized versions (uk, zh-cn, es,
pt-br, ko, pl).

packages/docs/content/docs/quickstart.mdx

@@ -1,22 +1,26 @@
 ---
 title: Quickstart
-description: Start OpenChamber quickly and choose the right surface for the task.
+description: Start OpenChamber quickly and pick the right app for the task.
 ---
 
 # Quickstart
 
 ## Fastest path
 
-1. Install OpenCode.
-2. Install OpenChamber CLI.
+1. Install [OpenCode](https://opencode.ai).
+2. Install the OpenChamber CLI (see [Install](/install/) for the one-line command).
 3. Run `openchamber --ui-password be-creative-here`.
-4. Open the web UI on your machine.
-5. If needed, start a tunnel and scan the QR code from your phone.
+4. Open the URL the CLI prints (usually `http://localhost:3000`).
+5. To use it from your phone, start a [tunnel](/tunnels/) and scan the QR code.
 
-Use a strong UI password, especially if you plan to expose the instance remotely.
+You should see the OpenChamber session list in your browser. If it loads, you're up and running.
 
-## Which surface should I use?
+Use a strong UI password, especially if you plan to open the instance to the internet.
 
-- use **desktop** for macOS-heavy daily driver workflows
-- use **web** for remote access and mobile review
-- use **VS Code** for editor-native sessions beside code
+If the page doesn't load, check [Troubleshooting](/troubleshooting/).
+
+## Which app should I use?
+
+- use **desktop** for day-to-day work on macOS
+- use **web** for remote access and reviewing from your phone
+- use **VS Code** for sessions right next to your code