feat(runner, cli): runner-side marker literals + the zero-trade walk-forward notice

Iteration stderr-markers-2, tasks 3-4 of the stderr-class-markers plan.

aura-runner's four continuing-run diagnostics join the class grammar as
hand-written literals (the #295 boundary keeps the macro owner in the
presentation crate): the stale-dylib warning gains the `aura: ` namespace,
and the three tap/no-nominee notices become `aura: note: ` — the latter
two extracted into pure note-builder fns with unit pins. The two e2e
pins on the cost-model tap string moved with the retag
(research_docs.rs). A new project_nodes e2e exercises the real stale-
dylib load path: fresh build emits nothing, a source newer than the
dylib emits exactly one class-marked warning and still succeeds.

The #313 notice ships on both walk-forward paths: `aura: note: all N
walk-forward windows recorded zero trades` before the summary JSON,
exit 0 untouched (a null result is a valid research result, #198).
Wording and condition live in one shared diag helper taking the
per-window trade counts (orchestrator tidy of the reviewer's
duplicated-predicate residue); the call sites keep only the
path-specific field extraction. Three e2es pin it: the equal-length
degenerate on the synthetic path (exactly one note, no warnings, exit
0, summary unchanged), a traded negative twin, and the real/sugar-path
degenerate gated on the GER40 archive.

refs #278, refs #313

crates/aura-cli/src/diag.rs

@@ -18,3 +18,15 @@ macro_rules! warning {
 }
 
 pub(crate) use {note, warning};
+
+/// The #313 zero-trade note, shared by both walk-forward paths (the
+/// synthetic-blueprint path in `main.rs` and the `--real` sugar path in
+/// `verb_sugar.rs`) so the wording AND the condition live in exactly one
+/// place. Takes the per-window trade counts; a no-op unless there is at
+/// least one window and every one of them traded zero times.
+pub(crate) fn note_zero_trade_windows(mut window_trades: impl ExactSizeIterator<Item = u64>) {
+    let n_windows = window_trades.len();
+    if n_windows > 0 && window_trades.all(|n| n == 0) {
+        note!("all {n_windows} walk-forward windows recorded zero trades");
+    }
+}

crates/aura-cli/src/main.rs

@@ -917,6 +917,12 @@ fn run_blueprint_walkforward(
     for w in &result.windows {
         println!("{}", family_member_line(&id, &w.run.oos_report));
     }
+    crate::diag::note_zero_trade_windows(
+        result
+            .windows
+            .iter()
+            .map(|w| w.run.oos_report.metrics.r.as_ref().map_or(0, |m| m.n_trades)),
+    );
     println!("{}", walkforward_summary_json(&result));
 }
 

crates/aura-cli/src/verb_sugar.rs

@@ -549,6 +549,9 @@ pub(crate) fn run_walkforward_sugar(
         summary_axes.push("stop_length".to_string());
         summary_axes.push("stop_k".to_string());
     }
+    crate::diag::note_zero_trade_windows(
+        wf.reports.iter().map(|r| r.metrics.r.as_ref().map_or(0, |m| m.n_trades)),
+    );
     println!("{}", crate::walkforward_summary_json_from_reports(&wf.reports, &summary_axes));
 
     // Trace persistence runs LAST (mirroring `present_campaign`'s ordering,