Add header and legend to session list output

src/cli.ts

@@ -216,6 +216,8 @@ program
     const cols = process.stdout.columns || 80
     const prefixWidth = branchWidth + 4
 
+    console.log(`  ${"BRANCH".padEnd(branchWidth)}  PROMPT`)
+
     for (const s of sessions) {
       const prompt = s.prompt ?? ""
       const icon = icons[statuses[s.branch]]
@@ -223,6 +225,8 @@ program
       const truncated = maxPrompt > 3 && prompt.length > maxPrompt ? prompt.slice(0, maxPrompt - 3) + "..." : prompt
       console.log(`${icon} ${s.branch.padEnd(branchWidth)}  ${truncated}`)
     }
+
+    console.log(`\n◌ idle · ◯ active · ◎ unsaved · ● saved`)
   })
 
 // ── sandlot open <branch> ─────────────────────────────────────────────