feat(proxy): add scoped proxy configuration and docs runbooks

- add scope-aware proxy schema and runtime wiring for providers/channels/tools

- add agent callable proxy_config tool for fast proxy setup

- standardize docs system with index, template, and playbooks

src/channels/slack.rs

@@ -6,7 +6,6 @@ pub struct SlackChannel {
     bot_token: String,
     channel_id: Option<String>,
     allowed_users: Vec<String>,
-    client: reqwest::Client,
 }
 
 impl SlackChannel {
@@ -15,10 +14,13 @@ impl SlackChannel {
             bot_token,
             channel_id,
             allowed_users,
-            client: reqwest::Client::new(),
         }
     }
 
+    fn http_client(&self) -> reqwest::Client {
+        crate::config::build_runtime_proxy_client("channel.slack")
+    }
+
     /// Check if a Slack user ID is in the allowlist.
     /// Empty list means deny everyone until explicitly configured.
     /// `"*"` means allow everyone.
@@ -29,7 +31,7 @@ impl SlackChannel {
     /// Get the bot's own user ID so we can ignore our own messages
     async fn get_bot_user_id(&self) -> Option<String> {
         let resp: serde_json::Value = self
-            .client
+            .http_client()
             .get("https://slack.com/api/auth.test")
             .bearer_auth(&self.bot_token)
             .send()
@@ -58,7 +60,7 @@ impl Channel for SlackChannel {
         });
 
         let resp = self
-            .client
+            .http_client()
             .post("https://slack.com/api/chat.postMessage")
             .bearer_auth(&self.bot_token)
             .json(&body)
@@ -108,7 +110,7 @@ impl Channel for SlackChannel {
             }
 
             let resp = match self
-                .client
+                .http_client()
                 .get("https://slack.com/api/conversations.history")
                 .bearer_auth(&self.bot_token)
                 .query(&params)
@@ -179,7 +181,7 @@ impl Channel for SlackChannel {
     }
 
     async fn health_check(&self) -> bool {
-        self.client
+        self.http_client()
             .get("https://slack.com/api/auth.test")
             .bearer_auth(&self.bot_token)
             .send()