audit: cycle 0024 (#43, #36) — drift-clean; ledger reconciled to the pre-build signature

Architect drift review (862882b..1b39093): NO code drift, no contract weakened.
C1 (behaviour-preserving: 150 tests green, render goldens byte-identical, no
behavioural assertion altered), C8 (sink output: vec![] preserved), C9/C23
(read-only render touches no eval/build; derive_signature's Box::leak is
cold-path-only, leaked names non-load-bearing) all hold. Regression scripts:
none configured (no-op) — the architect review is the gate.

The only drift was design-ledger prose, anticipated and deferred to this audit
by the plan. Resolved here (fix path, orchestrator-applied — docwriter is barred
from the design ledger):

- docs/design/INDEX.md C8 Guarantee: rewritten — a node's signature (NodeSchema)
  is declared pre-build on the value-empty recipe; the built node implements
  lookbacks() (the one param-dependent sizing quantity) + eval(); schema() is gone.
- INDEX.md C8 cycle-0015 note: Blueprint::param_space -> Composite::param_space;
  the #36 lockstep-debt clause marked closed by 0024.
- INDEX.md: added a C8 cycle-0024 realization (signature lives once on the recipe,
  the signature/sizing split, #43/#36 closed) and a C19 cycle-0024 realization
  (struct Blueprint collapsed into the root Composite; Role.source/runnable-iff-
  bound/UnboundRootRole; FlatGraph as the named compilat). Stale symbol names in
  the dated 0016/0017 notes annotated in place with their 0024 renames.
- aura-std/src/lincomb.rs module doc: Blueprint::param_space -> Composite::param_space.

Ledger-gap (four new load-bearing invariants previously unrecorded) closed by the
two new realization notes. Green baseline re-confirmed after the edits: cargo test
--workspace 150 passed / 0 failed; cargo clippy --all-targets -D warnings clean.

refs #43 #36

crates/aura-std/src/lincomb.rs

@@ -4,7 +4,7 @@
 //! weights are construction parameters that configure the node and fix its
 //! arity (`weights.len()` inputs); they are also the combination's tunable
 //! params, declared in the schema (cycle 0015) as `weights[0..N]` — N flat
-//! indexed `F64` knobs that `Blueprint::param_space` aggregates (C8/C12/C19).
+//! indexed `F64` knobs that `Composite::param_space` aggregates (C8/C12/C19).
 
 use aura_core::{
     Ctx, FieldSpec, Firing, Node, NodeSchema, ParamSpec, PortSpec, PrimitiveBuilder, Scalar,