audit: cycle 0104 tidy (drift-clean after three doc-mirror alignments)

Architect drift review (range d5c4361..45fb06d): drift_found, three items,
all doc-mirror — resolved inline as close-fixes:
- docs/design/INDEX.md — the two #171 deferral passages (C18 #158
  realization + C24 status) now record the shipped identity id (additive
  sibling; content id keeps the store/reproduce roles; introspection-only
  until a dedup consumer exists). Whole-harness / structural-axis
  content-addressing stays deferred.
- README.md — introspect table gains the --identity-id row incl. the
  combinable id-flag behaviour.
- docs/glossary.md — three record-reality entries: content id, identity id
  (Avoid: identity hash, topology-identity hash), topology hash; the
  README row aligned to the canonical term.

What holds (architect): additive-sibling discipline intact (no store code
touched, every content-id/topology_hash pin green); C23 honoured precisely
(each strip arm has a protecting property test; factoring byte-preserving
via the canonical golden); the two extra engine tests are genuinely
distinct coverage (recursion arm, role/output arms), no redundancy.

Regression gates (all green): cargo build clean; cargo test --workspace
884 passed / 0 failed (873 baseline + 11 new); clippy --all-targets
-D warnings clean; cargo doc --no-deps 0 warnings.

Ephemeral cycle artifacts removed per project convention (git rm):
docs/specs/0104-topology-identity-hash.md,
docs/plans/0104-topology-identity-hash.md.

refs #180

README.md

@@ -80,6 +80,7 @@ of by-identifier construction ops replayed against the standard node vocabulary.
 | `aura graph introspect --node <T>` | Show one type's input ports, output fields, and param paths (with the bind-value form). |
 | `aura graph introspect --unwired` | Read a *partial* op-list on stdin and list its still-open interior slots. |
 | `aura graph introspect --content-id` | Read an op-list on stdin and print the SHA-256 content id of the blueprint it would build. |
+| `aura graph introspect --identity-id` | Read an op-list on stdin and print the SHA-256 **identity id** — the topology's debug-name-blind id, so two documents (or an op-script and a Rust-built blueprint) expressing the same topology print the same id. Combinable with `--content-id` (both ids, one per line, content id first). |
 
 ### Op-list shape