Colony CLI: inbox + ack commands

- colony inbox [--json] — show unacked inbox items
- colony ack <id> [--all] [--quiet] — ack items
- Client methods: get_inbox(), ack_inbox()
- AckRequest gets Serialize derive for CLI use

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/colony-types/src/lib.rs

@@ -114,7 +114,7 @@ pub struct InboxQuery {
     pub user: String,
 }
 
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Serialize, Deserialize)]
 pub struct AckRequest {
     pub ids: Vec<i64>,
 }