hive-forge: add repo-labels verb to list a repo's full label set

`labels <number>` only lists an issue/PR's labels; there was no way to
list the project-wide label set, which triage/labelling needs to discover
valid names. Add `repo-labels [pattern]` hitting GET /repos/{owner}/{repo}/labels
(paginated), with optional name-substring filter. Default prints one label
per line (name + tab-separated description when set); --json emits the full
label objects.

hive-forge/src/verbs/mod.rs

@@ -31,6 +31,7 @@ pub mod pr_reviews;
 pub mod pr_status;
 pub mod repo_add_collaborator;
 pub mod repo_create;
+pub mod repo_labels;
 pub mod subscription;
 pub mod timeline;
 pub mod tree_sha;

hive-forge/src/verbs/repo_labels.rs

@@ -0,0 +1,52 @@
+//! `repo-labels [pattern]` — list the active repo's full label set
+//! (project-wide), not the labels on one issue/PR (that's `labels
+//! <number>`). Useful for triage / labelling to discover the valid label
+//! names + what each means before applying them.
+
+use anyhow::Result;
+use clap::Args as ClapArgs;
+use serde_json::{Value, json};
+
+use crate::client::Client;
+use crate::verbs::print_json;
+
+#[derive(ClapArgs)]
+pub struct Args {
+    /// Substring pattern to filter label names (case-sensitive).
+    pattern: Option<String>,
+}
+
+pub fn run(client: &Client, args: Args) -> Result<()> {
+    let repo = client.repo();
+    // Repos can carry more than one page of labels; paginate so the list
+    // is complete rather than capped at the first page.
+    let labels = client.get_json_all(&format!("/repos/{repo}/labels"), 10)?;
+    let filtered: Vec<&Value> = labels
+        .iter()
+        .filter(|l| {
+            let name = l.get("name").and_then(Value::as_str).unwrap_or_default();
+            args.pattern.as_deref().is_none_or(|p| name.contains(p))
+        })
+        .collect();
+
+    if client.json_mode() {
+        // Full label objects (id, name, color, description) as a JSON array.
+        print_json(&json!(filtered))?;
+    } else {
+        // One label per line: `name`, plus its description (tab-separated)
+        // when set, so triage can see what each label means at a glance.
+        for l in filtered {
+            let name = l.get("name").and_then(Value::as_str).unwrap_or_default();
+            let desc = l
+                .get("description")
+                .and_then(Value::as_str)
+                .unwrap_or_default();
+            if desc.is_empty() {
+                println!("{name}");
+            } else {
+                println!("{name}\t{desc}");
+            }
+        }
+    }
+    Ok(())
+}