test: red executable-spec for #264 cut 2 — aura data list enumerates symbols

aura data list must print the archive's symbols sorted, one per line,
exit 0 — the discovery step before aura data coverage. Hostless RED over
the synthetic SYMA+SYMB archive; fails on the absent 'list' subcommand
(clap exit 2), not on scaffolding.

refs #264

crates/aura-cli/tests/cli_run.rs

@@ -5904,3 +5904,36 @@ fn data_coverage_reports_month_span_and_interior_gap_range() {
         "first (2024-01) and last (2024-06) present month reported: {stdout}"
     );
 }
+
+/// Property (#264, list cut 2): `aura data list` enumerates the symbols the
+/// archive contains, one per line, sorted — the discovery step a campaign
+/// author (or an agent operating through the CLI alone, the deployment
+/// posture) needs before `aura data coverage <symbol>`, since without it the
+/// inventory is obtainable only by listing the archive directory outside
+/// aura. The archive root resolves through the same project path as `coverage`
+/// (`Env::data_path` — a project-local `[paths] data` override when set). Over
+/// a hermetic synthetic archive holding two symbols (`SYMA` 2024-01..08 and
+/// `SYMB` 2024-03..06), the verb exits 0 and prints EXACTLY the two symbol
+/// names in ascending order, one per line — `SYMA` before `SYMB`, nothing
+/// else.
+#[test]
+fn data_list_enumerates_archive_symbols_one_per_line_sorted() {
+    let (cwd, _g) = fresh_project_with_data();
+    let out = std::process::Command::new(env!("CARGO_BIN_EXE_aura"))
+        .args(["data", "list"])
+        .current_dir(&cwd)
+        .output()
+        .expect("spawn aura data list");
+    assert_eq!(
+        out.status.code(),
+        Some(0),
+        "exit: {:?}, stderr: {}",
+        out.status,
+        String::from_utf8_lossy(&out.stderr)
+    );
+    let stdout = String::from_utf8(out.stdout).expect("utf-8 stdout");
+    // The whole contract: the two archive symbols, sorted, one per line, and
+    // nothing else — this is the inventory a campaign author reads before
+    // scoping an instrument matrix.
+    assert_eq!(stdout, "SYMA\nSYMB\n", "sorted symbol enumeration: {stdout:?}");
+}