fix(aura-cli, aura-runner): review findings — duplicate --override refusal, live discovery prose, neutral JSON refusal

In-cycle fixes for the independent review of the #319 package, RED-first
for both Importants. A repeated --override path now refuses at the shared
lexer (exit 2, path named) instead of panicking exit 101 through
reopen_all — which also un-misattributes the campaign leg's collision
prose for duplicates. override_paths' refusal points at aura graph
introspect --params (the retired --list-axes reference swept from every
live comment, one explicitly-historical mention remains). exec classifies
file targets through a Result-bearing peek: unparseable JSON refuses
neutrally before any leg is chosen. RunPresentation (single-variant)
removed; run_campaign_returning's contract note names its one deliberate
usage-class exit; C14's routing sentence and C20's family-builder
paragraph amended to current truth (superseded text to the history
sidecars); bench error strings and deletion blank-line runs tidied.

refs #319

crates/aura-engine/src/blueprint.rs

@@ -574,7 +574,8 @@ pub enum ReopenError {
 
 /// One entry of the aggregated BOUND param surface (#246): the path-qualified
 /// twin of [`ParamSpec`] carrying the bound value — the default a sweep axis
-/// may override, and what `--list-axes` renders as `default=`.
+/// may override, and what `aura graph introspect --params` renders as
+/// `default=`.
 #[derive(Debug, Clone, PartialEq)]
 pub struct BoundSpec {
     pub name: String,
@@ -3376,7 +3377,8 @@ mod tests {
     }
 
     /// #246: bound_param_space mirrors param_space's path qualification and
-    /// carries the bound value (the default the CLI renders in --list-axes).
+    /// carries the bound value (the default the CLI renders in
+    /// `aura graph introspect --params`).
     #[test]
     fn bound_param_space_is_path_qualified_with_values() {
         use aura_strategy::Bias;