audit: cycle 0034 (#55) — record structural-constant bind in the ledger; drift-clean otherwise

Architect drift review over 52e0214..HEAD. All hard invariants hold; the only
drift was a ledger-prose gap — the new .bind() structural-constant affordance had
no contract entry, so the code offered a capability the contracts did not name.

Contracts (all hold):
- C23: bind resolves a param name -> position at authoring time and stores the
  index; the compilat stays wired by raw index, the name never reaches it. The
  by-name authoring address space (0032 amendment) is exactly where bind sits.
- C19/C8: the shrink is schema.params.remove(pos) on the single source of truth
  that params()/schema()/collect_params/lower_items all read, so no desync is
  structurally possible; param_space() injectivity (0032) is untouched (bind only
  removes entries). The param-declared-once posture holds.
- C9/C10: a pure builder-level value op — no by-name runtime node lookup, no
  registry, no DSL-style dynamic resolution.
- C16: zero Cargo.toml / lockfile changes.
- Construction layer (collect_params/lower_items/param_space/compile_with_params)
  byte-unchanged — verified independently; the blueprint.rs diff is a test-only
  hunk at 1886, the sole production edit is bind in aura-core/src/node.rs.

Regression: none configured (profile regression: []) — no-op; architect is the gate.

Resolution -- fix (1 ledger note, added inline this commit):
- docs/design/INDEX.md C19 — added a cycle-0034 realization note recording
  PrimitiveBuilder::bind as the structural-constant path (knob REMOVED from
  param_space), distinct from the cycle-0016 value-pin (knob stays, fixed in the
  injected vector); the #55 deform-vs-tune discriminator; C23 unaffected; export of
  a named frozen strategy deferred to #60.

Cycle 0034 drift-clean after this note. Not a milestone close (no milestone
fieldtest run). Gates: doc-only edit, compile-inert; cargo build/clippy/test
--workspace verified green this session.

docs/design/INDEX.md

@@ -742,6 +742,32 @@ notation — superseding the cycle-0017 flat-ascii model and its renderer-defect
 workaround. The DOT/SVG are Graphviz-version-dependent and not golden-tested; the
 deterministic JSON model is the asserted contract.
 
+**Realization (cycle 0034 — structural-constant bind: a knob *removed* from
+param_space, #55).** `PrimitiveBuilder::bind(slot, value)` adds the **third** param
+category beside the topology factory-arg (C7/C19) and the tuning param (the
+cycle-0016 value-pin): a **structural constant**. The cycle-0016 binding *pins* a
+value in the injected vector while the knob **stays** in `param_space` (a tuning
+param the sweep varies); `bind` instead **removes** the slot from `param_space`
+entirely — the knob is gone, not fixed. The discriminator is the #55
+deform-vs-tune test: a value whose variation yields another valid point of the
+*same* strategy is a **tuning param** (stays in `param_space`); a value whose
+variation *deforms* the strategy into a different one (e.g. the `2` of an
+"SMA2-entry" bound to its two-candle construction) is a **structural constant**
+(bound out), so a sweep never enumerates deformed strategies as valid family
+members. Mechanically `bind` shrinks the builder's declared param surface
+(`schema.params`) and wraps its build closure to re-splice the constant at its
+original positional slot; the construction layer
+(`collect_params`/`lower_items`/`param_space`/`compile_with_params`) is
+**byte-unchanged** — both dock sites already key off `builder.params()`, so the
+shrink propagates for free, and chained binds reconstruct the correct positional
+vector because each layer computes its slot index relative to the param list it
+sees. C23 is unaffected: `bind` resolves the param **name** to a position at
+**authoring** time (the by-name authoring address space, the 0032 amendment) and
+the compilat stays wired by raw index — the name never reaches it. The
+complementary question — exporting a **named frozen** strategy (all/most knobs
+bound) as a reusable blueprint *value* — is deferred (#60); `bind` ships only the
+per-knob overlay, no registry (C9/C10 intact).
+
 ### C20 — Strategy ↔ harness; the harness is the root sim graph
 **Guarantee.** A **strategy** is a reusable composite-node blueprint (C9):
 broker-, data-, and viz-independent, with inputs declared as named **roles**