feat(engine,cli): run manifests stamp untouched bound defaults (closes #249)

RunManifest gains defaults: Vec<(String, Scalar)> — the wrap-prefixed
bound_param_space() of the signal, read after axis reopening, so a
bound param an axis overrode has already left the space and flows
through params instead (disjoint by construction; verified end to end:
a sweep member's overridden fast.length sits in params while
slow.length/bias.scale sit in defaults). params keeps its "what varied"
semantics and stays the reproduce input. One-directional serde
widening (#[serde(default)]) per the selection/instrument/topology_hash
idiom — old records deserialize with an empty defaults; unlike the
Option fields it always serializes, mirroring params. ~20
struct-literal sites across five crates gained the field
(compile-mandated breadth, no behaviour change at those sites).

The C14 ledger records the underlying decision (2026-07-13): generated
outcome records spend redundancy on direct readability (single writer,
cannot drift); authored intent artifacts admit none (every redundancy
is a drift site) — so the fix lands in the manifest, never the
blueprint.

Verification: RED test run_manifest_stamps_untouched_bound_defaults
green; cargo build --workspace; cargo test --workspace green; clippy
-D warnings on the touched crates; binary-level sweep exclusivity
check.

crates/aura-campaign/src/exec.rs

@@ -554,6 +554,7 @@ fn placeholder_report(params: &[(String, Scalar)], window_ms: (i64, i64)) -> Run
         manifest: RunManifest {
             commit: String::new(),
             params: params.to_vec(),
+            defaults: Vec::new(),
             window: (Timestamp(window_ms.0), Timestamp(window_ms.1)),
             seed: 0,
             broker: "faulted-member-placeholder".to_string(),

crates/aura-campaign/src/lib.rs

@@ -339,6 +339,7 @@ mod tests {
             manifest: RunManifest {
                 commit: "test".to_string(),
                 params: vec![],
+                defaults: vec![],
                 window: (Timestamp(0), Timestamp(1)),
                 seed: 0,
                 broker: "sim".to_string(),
@@ -1019,6 +1020,7 @@ mod wf_tests {
                 manifest: RunManifest {
                     commit: "wf-fake".to_string(),
                     params: params.to_vec(),
+                    defaults: Vec::new(),
                     window: (Timestamp(window_ms.0), Timestamp(window_ms.1)),
                     seed: 0,
                     broker: "fake".to_string(),

crates/aura-campaign/tests/execute.rs

@@ -58,6 +58,7 @@ fn planted_report(cell: &CellSpec, params: &[(String, Scalar)], window_ms: (i64,
         manifest: RunManifest {
             commit: "fake".to_string(),
             params: params.to_vec(),
+            defaults: Vec::new(),
             window: (Timestamp(window_ms.0), Timestamp(window_ms.1)),
             seed: 0,
             broker: "fake".to_string(),

crates/aura-campaign/tests/member_seam_e2e.rs

@@ -46,6 +46,7 @@ impl MemberRunner for FixedRunner {
             manifest: RunManifest {
                 commit: "e2e".to_string(),
                 params: vec![],
+                defaults: vec![],
                 window: (Timestamp(window_ms.0), Timestamp(window_ms.1)),
                 seed: 0,
                 broker: "test".to_string(),
@@ -98,6 +99,7 @@ fn rankable_metrics_are_all_per_member_resolvable() {
         manifest: RunManifest {
             commit: "e2e".to_string(),
             params: vec![],
+            defaults: vec![],
             window: (Timestamp(0), Timestamp(1)),
             seed: 0,
             broker: "test".to_string(),