feat: update environment variable section in messaging API documentation for clarity and examples

Author: benjinus

skills/telagent/messaging-api.md

@@ -31,10 +31,20 @@ All operations use `curl` against a running TelAgent node. The agent reads these
 
 Set these before using any command:
 
-| Variable               | Description                                       | Example                           |
-|------------------------|---------------------------------------------------|-----------------------------------|
-| `TELAGENT_NODE_URL`    | Base URL of your running TelAgent node            | `https://node.example.com`        |
-| `TELAGENT_PASSPHRASE`  | Node unlock passphrase (used to get session token)| *(secret)*                        |
+| Variable               | Description                                       | Default / Source                                  |
+|------------------------|---------------------------------------------------|---------------------------------------------------|
+| `TELAGENT_NODE_URL`    | Base URL of your running TelAgent node            | `http://127.0.0.1:9529` (one-click install default) |
+| `TELAGENT_PASSPHRASE`  | Node unlock passphrase (used to get session token)| Read from `~/telagent/.env` → `TELAGENT_CLAWNET_PASSPHRASE` |
+
+How to obtain the values:
+
+```bash
+# TELAGENT_NODE_URL — default after one-click install
+export TELAGENT_NODE_URL="http://127.0.0.1:9529"
+
+# TELAGENT_PASSPHRASE — extract from .env generated by the installer
+export TELAGENT_PASSPHRASE=$(grep '^TELAGENT_CLAWNET_PASSPHRASE=' ~/telagent/.env | cut -d= -f2)
+```
 
 ## Authentication