docs(installation): drop Claude CLI prereq, document /start and /login

The Agent SDK now bundles the Claude Code CLI, so users no longer
need to install it separately. Replace the prerequisite with a brief
note pointing to /login (OAuth via Mini App) or ANTHROPIC_API_KEY,
and add an "Authenticate Claude" section covering /start and /login.
Also fix the config path to cover both Linux and macOS.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: yjwong

website/src/content/docs/getting-started/installation.md

@@ -7,17 +7,7 @@ sidebar:
 
 ## Prerequisites
 
-- **Claude CLI** — the Anthropic Claude Code CLI, installed and authenticated
-
-### Install and authenticate Claude CLI
-
-Follow the [official instructions](https://docs.anthropic.com/en/docs/claude-code/getting-started) to install Claude Code. Then authenticate:
-
-```bash
-claude  # follow the prompts to log in
-```
-
-You can also set `ANTHROPIC_API_KEY` in your environment if you prefer API key authentication.
+OpenShrimp bundles the Claude Code CLI via the Agent SDK, so there's nothing to install separately. You just need to authenticate Claude — either by running `/login` from inside the bot (see [Authenticate Claude](#authenticate-claude) below), or by setting `ANTHROPIC_API_KEY` in your environment.
 
 ## Download
 
@@ -59,10 +49,6 @@ On macOS, OpenShrimp is also available as a menu bar app. Download the `.dmg` fr
 - Start/stop the bot, open config, view logs — all from the menu bar
 - "Start at Login" toggle for automatic launch
 
-:::note
-The macOS app is currently unsigned. On first launch, macOS will block it — right-click the app and choose "Open" to bypass Gatekeeper, or go to System Settings → Privacy & Security and click "Open Anyway".
-:::
-
 ## Run the setup wizard
 
 On first run, the binary launches an interactive setup wizard:
@@ -77,10 +63,16 @@ The wizard walks you through:
 2. Your Telegram user ID (from [@userinfobot](https://t.me/userinfobot))
 3. Creating your first context (project directory, description, model)
 
-It writes the config to `~/.config/openshrimp/config.yaml`. You can also set this up manually — see [Configuration](/getting-started/configuration/).
+It writes the config to a platform-specific location (`~/.config/openshrimp/config.yaml` on Linux, `~/Library/Application Support/openshrimp/config.yaml` on macOS). You can also set this up manually — see [Configuration](/getting-started/configuration/).
 
 On subsequent runs, the binary starts instantly.
 
+## Authenticate Claude
+
+Once the bot is running, open it in Telegram and send `/start` to see a welcome message confirming you're connected and showing your current context.
+
+If you haven't set `ANTHROPIC_API_KEY`, send `/login` (in a private chat) to authenticate Claude Code via OAuth. This opens a Mini App that runs the same OAuth flow you'd get from the Claude Code CLI — paste the resulting token to finish login. Use `/login` again any time you need to re-authenticate.
+
 ## Building from source
 
 If you need to build from source (older Linux distros, development, etc.), see [Building from Source](/reference/building-from-source/).