feat(aura-cli): aura runs registry — persist on sweep, list + rank (cycle D / iter 3)

Final iteration of the run-registry cycle (#33): the read surface that makes a
sweep family — and runs across separate invocations — comparable over time
(C18's "compare experiments over time", which has no home in git or Gitea).

- `aura sweep` now persists each point's RunReport to runs/runs.jsonl (append-
  only, one serde_json line per run) in addition to printing it.
- `aura runs list` prints every stored record, in store order.
- `aura runs rank <metric>` prints the stored runs best-first by the metric
  (total_pips desc; max_drawdown / exposure_sign_flips asc); an unknown metric
  is a usage error (exit 2), like every other aura arg error.

sweep_report splits into a production sweep_family() (the pure run) and a
#[cfg(test)] renderer kept for the in-bin goldens; the dispatch gains run_sweep
/ runs_list / runs_rank over default_registry() (runs/runs.jsonl under cwd).
Process goldens run the binary in a temp cwd so persistence never dirties the
repo; /runs/ is git-ignored as a backstop.

Verified end-to-end: two `aura sweep` invocations accumulate 8 records;
`aura runs list` shows all 8; `aura runs rank total_pips` orders them best-first;
`aura runs rank bogus` exits 2 with the known-metrics hint. cargo test
--workspace green (cli_run 11, registry 5, engine 93, …); clippy
--workspace --all-targets -D warnings clean; no stray runs/ in the work tree.

refs #33

crates/aura-cli/tests/cli_run.rs

@@ -7,6 +7,16 @@ use std::process::Command;
 /// crate; the binary is named `aura` in `Cargo.toml`).
 const BIN: &str = env!("CARGO_BIN_EXE_aura");
 
+/// A fresh, unique working directory for a process test that persists run
+/// records (so `aura sweep`'s `./runs/runs.jsonl` never dirties the repo).
+/// Unique per test + per process; no external tempfile dependency.
+fn temp_cwd(name: &str) -> std::path::PathBuf {
+    let dir = std::env::temp_dir().join(format!("aura-cli-{}-{}", std::process::id(), name));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).expect("create temp cwd");
+    dir
+}
+
 #[test]
 fn run_prints_json_and_exits_zero() {
     let out = Command::new(BIN).arg("run").output().expect("spawn aura run");
@@ -190,12 +200,11 @@ fn graph_emits_self_contained_html_viewer() {
 
 #[test]
 fn sweep_prints_four_json_lines_and_exits_zero() {
-    let out = Command::new(BIN).arg("sweep").output().expect("spawn aura sweep");
+    let cwd = temp_cwd("sweep4");
+    let out = Command::new(BIN).arg("sweep").current_dir(&cwd).output().expect("spawn aura sweep");
     assert!(out.status.success(), "exit status: {:?}", out.status);
 
     let stdout = String::from_utf8(out.stdout).expect("utf-8 stdout");
-    // one JSON line per grid point (4-point built-in grid), each terminated by a
-    // newline from `sweep_report`.
     assert_eq!(stdout.lines().count(), 4, "stdout was: {stdout:?}");
     let first = stdout.lines().next().unwrap();
     // each line is a full RunReport; commit is the real git HEAD (volatile), so
@@ -205,6 +214,7 @@ fn sweep_prints_four_json_lines_and_exits_zero() {
         first.contains("\"params\":{\"sma_cross.fast\":2,\"sma_cross.slow\":4,\"scale\":0.5}"),
         "got: {stdout}"
     );
+    let _ = std::fs::remove_dir_all(&cwd);
 }
 
 #[test]
@@ -213,3 +223,59 @@ fn sweep_with_trailing_token_is_strict_and_exits_two() {
     let out = Command::new(BIN).args(["sweep", "extra"]).output().expect("spawn aura");
     assert_eq!(out.status.code(), Some(2), "exit status: {:?}", out.status);
 }
+
+#[test]
+fn runs_list_and_rank_across_invocations() {
+    let cwd = temp_cwd("runs-flow");
+    // two sweeps accumulate 8 records over time
+    for _ in 0..2 {
+        let out = Command::new(BIN).arg("sweep").current_dir(&cwd).output().expect("spawn sweep");
+        assert!(out.status.success(), "sweep exit: {:?}", out.status);
+    }
+
+    // `runs list` shows all 8 stored records
+    let list = Command::new(BIN).args(["runs", "list"]).current_dir(&cwd).output().expect("spawn list");
+    assert!(list.status.success(), "list exit: {:?}", list.status);
+    let list_out = String::from_utf8(list.stdout).expect("utf-8");
+    assert_eq!(list_out.lines().count(), 8, "list: {list_out:?}");
+    assert!(list_out.lines().all(|l| l.starts_with("{\"manifest\":{")), "list shape: {list_out:?}");
+
+    // `runs rank total_pips`: 8 lines, highest total_pips first
+    let rank = Command::new(BIN).args(["runs", "rank", "total_pips"]).current_dir(&cwd).output().expect("spawn rank");
+    assert!(rank.status.success(), "rank exit: {:?}", rank.status);
+    let rank_out = String::from_utf8(rank.stdout).expect("utf-8");
+    assert_eq!(rank_out.lines().count(), 8, "rank: {rank_out:?}");
+    let pips: Vec<f64> = rank_out
+        .lines()
+        .map(|l| {
+            let key = "\"total_pips\":";
+            let start = l.find(key).expect("line has total_pips") + key.len();
+            let tail = &l[start..];
+            let end = tail.find([',', '}']).expect("token end");
+            tail[..end].parse().expect("total_pips is an f64")
+        })
+        .collect();
+    assert!(pips.windows(2).all(|w| w[0] >= w[1]), "rank not descending: {pips:?}");
+
+    // unknown metric is a usage error
+    let bogus = Command::new(BIN).args(["runs", "rank", "bogus"]).current_dir(&cwd).output().expect("spawn bogus");
+    assert_eq!(bogus.status.code(), Some(2), "bogus exit: {:?}", bogus.status);
+
+    let _ = std::fs::remove_dir_all(&cwd);
+}
+
+#[test]
+fn runs_list_on_empty_registry_is_zero_lines_exit_zero() {
+    let cwd = temp_cwd("runs-empty");
+    let out = Command::new(BIN).args(["runs", "list"]).current_dir(&cwd).output().expect("spawn list");
+    assert!(out.status.success(), "list exit: {:?}", out.status);
+    assert_eq!(out.stdout.len(), 0, "expected no output, got: {:?}", out.stdout);
+    let _ = std::fs::remove_dir_all(&cwd);
+}
+
+#[test]
+fn runs_bare_subcommand_is_strict_and_exits_two() {
+    // `aura runs` with no/unknown sub-subcommand is a usage error (#16 strict).
+    let out = Command::new(BIN).arg("runs").output().expect("spawn aura runs");
+    assert_eq!(out.status.code(), Some(2), "exit status: {:?}", out.status);
+}