fix(output): emit array-of-objects for JSON output

sessions list/dump and agents list/dump were passing Vec<Vec<String>>
directly to render_json, producing unlabeled arrays. Now each row is
mapped to a serde_json object with named keys before serializing.

Closes claudbg-pfa5

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.beans/claudbg-pfa5--json-output-is-array-of-arrays-instead-of-array-of.md

@@ -1,11 +1,11 @@
 ---
 # claudbg-pfa5
 title: JSON output is array-of-arrays instead of array-of-objects
-status: todo
+status: completed
 type: bug
 priority: normal
 created_at: 2026-03-30T04:37:05Z
-updated_at: 2026-03-30T04:41:14Z
+updated_at: 2026-03-30T05:05:12Z
 parent: claudbg-tci9
 ---
 
@@ -38,3 +38,7 @@ Output should be an array of objects with named keys:
 
 - `src/commands/sessions.rs` — `list()` and `dump()` JSON output branches
 - `src/output/json.rs` — generic `render_json`
+
+## Summary of Changes
+
+Fixed JSON output in both sessions.rs and agents.rs to produce array-of-objects instead of array-of-arrays. Each row is now mapped to a serde_json object with named keys before serializing. Keys: sessions list (id, date, project, model, messages, subagents), sessions dump (seq, timestamp, type, role, content), agents list (id, type, file, modified), agents dump (seq, timestamp, type, role, content).

src/commands/agents.rs

@@ -185,7 +185,20 @@ pub async fn list(session_id: &str, opts: &crate::cli::GlobalOpts) -> Result<()>
         crate::cli::OutputFormat::Table => {
             crate::output::render_table(&["Agent ID", "Type", "File", "Modified"], &rows)?
         }
-        crate::cli::OutputFormat::Json => crate::output::render_json(&rows)?,
+        crate::cli::OutputFormat::Json => {
+            let objects: Vec<serde_json::Value> = rows
+                .iter()
+                .map(|r| {
+                    serde_json::json!({
+                        "id":       r[0],
+                        "type":     r[1],
+                        "file":     r[2],
+                        "modified": r[3],
+                    })
+                })
+                .collect();
+            crate::output::render_json(&objects)?
+        }
         crate::cli::OutputFormat::Xml => {
             crate::output::render_xml_rows(&["agent_id", "type", "file", "modified"], &rows)?
         }
@@ -239,7 +252,21 @@ pub async fn dump(
         crate::cli::OutputFormat::Table => {
             crate::output::render_table(&["#", "Timestamp", "Type", "Role", "Content"], &rows)?
         }
-        crate::cli::OutputFormat::Json => crate::output::render_json(&rows)?,
+        crate::cli::OutputFormat::Json => {
+            let objects: Vec<serde_json::Value> = rows
+                .iter()
+                .map(|r| {
+                    serde_json::json!({
+                        "seq":       r[0],
+                        "timestamp": r[1],
+                        "type":      r[2],
+                        "role":      r[3],
+                        "content":   r[4],
+                    })
+                })
+                .collect();
+            crate::output::render_json(&objects)?
+        }
         crate::cli::OutputFormat::Xml => {
             crate::output::render_xml_rows(&["seq", "timestamp", "type", "role", "content"], &rows)?
         }

src/commands/sessions.rs

@@ -202,7 +202,22 @@ pub async fn list(opts: &crate::cli::GlobalOpts) -> Result<()> {
         crate::cli::OutputFormat::Table => {
             crate::output::render_table(&["ID", "Date", "Project", "Model", "Messages"], &rows)?
         }
-        crate::cli::OutputFormat::Json => crate::output::render_json(&rows)?,
+        crate::cli::OutputFormat::Json => {
+            let objects: Vec<serde_json::Value> = rows
+                .iter()
+                .map(|r| {
+                    serde_json::json!({
+                        "id":       r[0],
+                        "date":     r[1],
+                        "project":  r[2],
+                        "model":    r[3],
+                        "messages": r[4],
+                        "subagents": 0,
+                    })
+                })
+                .collect();
+            crate::output::render_json(&objects)?
+        }
         crate::cli::OutputFormat::Xml => crate::output::render_xml_rows(
             &["session_id", "date", "project", "model", "messages"],
             &rows,
@@ -293,7 +308,21 @@ pub async fn dump(id: &str, follow: bool, opts: &crate::cli::GlobalOpts) -> Resu
         crate::cli::OutputFormat::Table => {
             crate::output::render_table(&["#", "Timestamp", "Type", "Role", "Content"], &rows)?
         }
-        crate::cli::OutputFormat::Json => crate::output::render_json(&rows)?,
+        crate::cli::OutputFormat::Json => {
+            let objects: Vec<serde_json::Value> = rows
+                .iter()
+                .map(|r| {
+                    serde_json::json!({
+                        "seq":       r[0],
+                        "timestamp": r[1],
+                        "type":      r[2],
+                        "role":      r[3],
+                        "content":   r[4],
+                    })
+                })
+                .collect();
+            crate::output::render_json(&objects)?
+        }
         crate::cli::OutputFormat::Xml => {
             crate::output::render_xml_rows(&["seq", "timestamp", "type", "role", "content"], &rows)?
         }