docs: continue onboarding terminology cleanup (#22535)

* docs: fix thinking link and add reasoning anchor reference

* docs(channels): rename LINE setup heading to onboarding

* docs(channels): normalize Nextcloud Talk onboarding headings

* docs(channels): use onboarding heading for Matrix setup

* docs(channels): standardize Discord onboarding heading

* docs(channels): standardize Telegram onboarding heading

* docs(channels): standardize WhatsApp onboarding heading

* docs(channels): rename iMessage onboarding and configuration sections

* docs(channels): rename Slack onboarding and configuration sections

* docs(channels): rename Signal onboarding heading

* docs(channels): standardize Nostr onboarding and configuration headings

* docs(channels): standardize Zalo onboarding and configuration headings

* docs(channels): standardize Twitch onboarding heading

docs/channels/nostr.md

@@ -40,7 +40,7 @@ openclaw plugins install --link <path-to-openclaw>/extensions/nostr
 
 Restart the Gateway after installing or enabling plugins.
 
-## Quick setup
+## Onboarding
 
 1. Generate a Nostr keypair (if needed):
 
@@ -69,7 +69,7 @@ export NOSTR_PRIVATE_KEY="nsec1..."
 
 4. Restart the Gateway.
 
-## Configuration reference
+## Configuration
 
 | Key          | Type     | Default                                     | Description                         |
 | ------------ | -------- | ------------------------------------------- | ----------------------------------- |

docs/channels/twitch.md

@@ -27,7 +27,7 @@ openclaw plugins install ./extensions/twitch
 
 Details: [Plugins](/tools/plugin)
 
-## Quick setup (beginner)
+## Onboarding
 
 1. Create a dedicated Twitch account for the bot (or use an existing account).
 2. Generate credentials: [Twitch Token Generator](https://twitchtokengenerator.com/)

docs/channels/zalo.md

@@ -17,7 +17,7 @@ Zalo ships as a plugin and is not bundled with the core install.
 - Or select **Zalo** during onboarding and confirm the install prompt
 - Details: [Plugins](/tools/plugin)
 
-## Quick setup (beginner)
+## Onboarding
 
 1. Install the Zalo plugin:
    - From a source checkout: `openclaw plugins install ./extensions/zalo`
@@ -161,7 +161,7 @@ Multi-account support: use `channels.zalo.accounts` with per-account tokens and
 - Confirm the gateway HTTP endpoint is reachable on the configured path
 - Check that getUpdates polling is not running (they're mutually exclusive)
 
-## Configuration reference (Zalo)
+## Configuration
 
 Full configuration: [Configuration](/gateway/configuration)