feat(aura-runner): skipped-tap note; undeclared-tap refusal enumerates declared taps

Two fold-selector fieldtest findings on the --tap seam, RED-first.

Skipped-tap note (#334): an explicit --tap plan replaces the record-all
default entirely (C27: unbound is inert) but gave no runtime signal that
unlisted declared taps went unbound — a forgotten tap surfaced only as a
missing trace file. bind_tap_plan's unbound arm now emits the C14 benign
note (aura: note: declared tap "<name>" unbound this run) per skipped
tap, exit unaffected. No new carrier: the arm is only reachable when
plan.default_named is None (an explicit plan) — under record-all it is
structurally dead, so the default emits nothing. Emitted runner-side
beside the existing eprintln registers; the runner->CLI print migration
is #297.

Undeclared-tap refusal (#333): --tap on a tap the blueprint does not
declare was refused without naming the valid taps, forcing the author
back into the blueprint JSON. TapPlanError::UnknownTap now carries the
declared-tap roster and Display appends it, mirroring UnknownLabel's
fold-roster idiom (C29: a refusal names the closed set it checks
against). Decision minuted on #333 (refusal roster over a new introspect
view).

Rider (#335): the fold roster doc lines now state the summary-row
timestamp — the accumulator folds (count/sum/mean/min/max) land one row
at the last warm (contributing) value's ts, and last gains the same
at-its-own-timestamp wording first already carried. The ratification
record lands in the sibling ledger/glossary commit.

closes #334
closes #333

crates/aura-cli/tests/tap_recording.rs

@@ -322,13 +322,17 @@ fn run_tap_selector_refuses_an_unknown_label_with_the_roster() {
     assert!(!cwd.join("runs").exists(), "a refused run must not write the store");
 }
 
-/// #310: a selection naming a tap the blueprint does not declare is
-/// refused typed (UndeclaredTap), before any store write.
+/// #310/#333: a selection naming a tap the blueprint does not declare is
+/// refused typed (UndeclaredTap), before any store write, and the refusal
+/// enumerates the blueprint's declared taps (the same way the unknown-fold
+/// refusal enumerates the fold-registry roster) — on the two-tap fixture,
+/// both `fast_tap` and `slow_tap` must be named so the author does not have
+/// to reopen the blueprint JSON.
 #[test]
 fn run_tap_selector_refuses_an_undeclared_tap() {
     let cwd = temp_cwd("tap-selector-undeclared");
-    let bp_path = cwd.join("tapped_r_sma.json");
-    std::fs::write(&bp_path, tap_blueprint_json()).expect("write tapped blueprint");
+    let bp_path = cwd.join("two_tap.json");
+    std::fs::write(&bp_path, two_tap_blueprint_json()).expect("write two-tap blueprint");
     let out = Command::new(BIN)
         .args(["run", bp_path.to_str().expect("utf-8 path"), "--tap", "nope=mean"])
         .current_dir(&cwd)
@@ -337,9 +341,61 @@ fn run_tap_selector_refuses_an_undeclared_tap() {
     assert!(!out.status.success(), "an undeclared tap must refuse");
     let stderr = String::from_utf8_lossy(&out.stderr);
     assert!(stderr.contains("nope"), "refusal must name the offending tap: {stderr}");
+    assert!(
+        stderr.contains("fast_tap") && stderr.contains("slow_tap"),
+        "refusal must enumerate the blueprint's declared taps: {stderr}"
+    );
     assert!(!cwd.join("runs").exists(), "a refused run must not write the store");
 }
 
+/// #334: an explicit `--tap` plan that leaves a declared tap unbound emits
+/// the C14 benign skipped-tap note on stderr, per unbound tap, naming it —
+/// exit code stays 0 (this is a note, not a refusal). `fast_tap` (subscribed)
+/// gets no such note; `slow_tap` (left unlisted) does.
+#[test]
+fn run_tap_selector_notes_unbound_declared_taps_on_stderr() {
+    let cwd = temp_cwd("tap-selector-unbound-note");
+    let bp_path = cwd.join("two_tap.json");
+    std::fs::write(&bp_path, two_tap_blueprint_json()).expect("write two-tap blueprint");
+
+    let out = Command::new(BIN)
+        .args(["run", bp_path.to_str().expect("utf-8 path"), "--tap", "fast_tap=mean"])
+        .current_dir(&cwd)
+        .output()
+        .expect("spawn aura run");
+    assert!(out.status.success(), "stderr: {}", String::from_utf8_lossy(&out.stderr));
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert!(
+        stderr.contains("aura: note: declared tap \"slow_tap\" unbound this run"),
+        "stderr must note the unbound declared tap: {stderr}"
+    );
+    assert!(
+        !stderr.contains("\"fast_tap\" unbound"),
+        "the subscribed tap must not be noted as unbound: {stderr}"
+    );
+}
+
+/// #334: the record-all default (no `--tap` flag) leaves no declared tap
+/// unbound — nothing is skipped, so the note must never appear.
+#[test]
+fn run_with_no_tap_flag_emits_no_unbound_note() {
+    let cwd = temp_cwd("tap-selector-default-no-note");
+    let bp_path = cwd.join("two_tap.json");
+    std::fs::write(&bp_path, two_tap_blueprint_json()).expect("write two-tap blueprint");
+
+    let out = Command::new(BIN)
+        .args(["run", bp_path.to_str().expect("utf-8 path")])
+        .current_dir(&cwd)
+        .output()
+        .expect("spawn aura run");
+    assert!(out.status.success(), "stderr: {}", String::from_utf8_lossy(&out.stderr));
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert!(
+        !stderr.contains("unbound this run"),
+        "the record-all default must never note a skipped tap: {stderr}"
+    );
+}
+
 /// #310: a malformed or duplicate `--tap` is a usage error (exit 2)
 /// before anything runs.
 #[test]

crates/aura-runner/src/member.rs

@@ -1728,9 +1728,14 @@ mod tests {
             Ok(_) => panic!("unknown tap must be refused"),
         };
         assert!(
-            matches!(err, TapPlanError::UnknownTap { ref name } if name == "no_such_tap"),
+            matches!(err, TapPlanError::UnknownTap { ref name, .. } if name == "no_such_tap"),
             "{err:?}"
         );
+        let msg = err.to_string();
+        assert!(
+            msg.contains("fast_tap"),
+            "unknown-tap refusal enumerates the declared taps (fixture declares only fast_tap): {msg}"
+        );
 
         // Unknown label — the refusal enumerates the roster.
         let mut flat2 = tapped_r_sma().compile_with_params(&[]).expect("tapped r_sma compiles");

crates/aura-runner/src/tap_plan.rs

@@ -161,17 +161,21 @@ impl FoldRegistry {
             }),
         });
         for (label, doc, fold) in [
-            ("count", "number of warm rows (any kind; i64 row)", FoldKind::Count),
-            ("sum", "sum of the series (f64 taps; f64 row)", FoldKind::Sum),
-            ("mean", "arithmetic mean of the series (f64 taps; f64 row)", FoldKind::Mean),
-            ("min", "minimum of the series (f64 taps; f64 row)", FoldKind::Min),
-            ("max", "maximum of the series (f64 taps; f64 row)", FoldKind::Max),
+            ("count", "number of warm rows (any kind; i64 row); one row at the last warm ts", FoldKind::Count),
+            ("sum", "sum of the series (f64 taps; f64 row); one row at the last warm ts", FoldKind::Sum),
+            (
+                "mean",
+                "arithmetic mean of the series (f64 taps; f64 row); one row at the last warm ts",
+                FoldKind::Mean,
+            ),
+            ("min", "minimum of the series (f64 taps; f64 row); one row at the last warm ts", FoldKind::Min),
+            ("max", "maximum of the series (f64 taps; f64 row); one row at the last warm ts", FoldKind::Max),
             (
                 "first",
                 "first warm value, at its own timestamp (any kind; kind-preserving row)",
                 FoldKind::First,
             ),
-            ("last", "last warm value (any kind; kind-preserving row)", FoldKind::Last),
+            ("last", "last warm value, at its own timestamp (any kind; kind-preserving row)", FoldKind::Last),
         ] {
             r.register(FoldEntry {
                 label,
@@ -217,7 +221,7 @@ impl FoldRegistry {
 /// `aura: ` + exit-1 refusal register via `Display`.
 pub enum TapPlanError {
     /// The plan names a tap the blueprint does not declare.
-    UnknownTap { name: String },
+    UnknownTap { name: String, declared: Vec<String> },
     /// The plan names a label the registry does not carry.
     UnknownLabel { label: String, roster: Vec<&'static str> },
     /// The entry's bind rule rejects the tap's column kind.
@@ -237,8 +241,12 @@ pub enum TapPlanError {
 impl fmt::Display for TapPlanError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            TapPlanError::UnknownTap { name } => {
-                write!(f, "the tap plan names '{name}', but the blueprint declares no such tap")
+            TapPlanError::UnknownTap { name, declared } => {
+                write!(
+                    f,
+                    "the tap plan names '{name}', but the blueprint declares no such tap — declared taps: {}",
+                    declared.join(", ")
+                )
             }
             TapPlanError::UnknownLabel { label, roster } => {
                 write!(f, "unknown fold '{label}' — available: {}", roster.join(", "))
@@ -402,7 +410,10 @@ pub fn bind_tap_plan(
     // Unknown-tap guard: every plan name must be declared.
     for name in plan.by_name.keys() {
         if !declared_taps.iter().any(|t| &t.name == name) {
-            return Err(TapPlanError::UnknownTap { name: name.clone() });
+            return Err(TapPlanError::UnknownTap {
+                name: name.clone(),
+                declared: declared_taps.iter().map(|t| t.name.clone()).collect(),
+            });
         }
     }
 
@@ -422,7 +433,18 @@ pub fn bind_tap_plan(
                 Some((label, params)) => {
                     Resolved::Named { label: label.clone(), params: params.clone() }
                 }
-                None => continue, // unbound, inert (C27)
+                // Unbound, inert (C27) — but only reachable when `plan` carries
+                // no default (an EXPLICIT plan, e.g. from `--tap`): record-all
+                // (`default_named` = `Some(("record", …))`) always resolves the
+                // Some arm above, so this arm never fires under record-all and
+                // the note is exactly the C14 benign skipped-tap class (#334).
+                // Emitted here (aura-runner), beside the pre-existing
+                // runner-side `eprintln!` registers in this module/`member.rs`/
+                // `measure.rs` — the runner→CLI print migration is #297.
+                None => {
+                    eprintln!("aura: note: declared tap \"{}\" unbound this run", tap.name);
+                    continue;
+                }
             },
         };
         if let Resolved::Named { label, params } = &sub {