audit: #271 cycle close — C24 reconciled with its own args paragraphs

Architect drift review (fable gate) on 26b3d68..HEAD, full diff read.
What holds: invariant 4 stays clean (ArgKind a separate closed enum at
every surface), minuted scope held (aura-research and SessionFrankfurt
untouched, no matrix surfacing), C18/C19 discipline held (args-free
bytes golden-pinned at v1, args id-bearing, no pending builder reaches
a graph on op or load path).

Fixed here (high/medium items): C24's out-of-the-round-trippable-set
paragraph still listed LinComb/CostSum/Session — now records their
#271 entry, with SimBroker as the remaining (scalar-typed, narrower)
exclusion; the pre-ship-dormancy paragraph's 'first ship freezes v1'
sentence stales against the shipped data-driven v2 writer — the
dormancy is recorded as ended by #271, the first exercised Tier-2 bump.

Routed (low items): #341 — refuse serializing a still-pending builder
on the Rust path (silent unloadable v1 artifact); version-refusal
prose prints only the ceiling.

Regression: aura-bench all five surfaces fingerprint OK, deltas within
noise (max +2.3% wall at loadavg 2.7, report-only) — the hot path is
untouched by design (bootstrap-only channel). Full workspace suite
independently re-run by the orchestrator: test-exit 0. Spec and plan
swept per lifecycle.

refs #271, refs #341

docs/design/contracts/c24-blueprint-data.md

@@ -70,8 +70,10 @@ loop for the round-trippable vocabulary.
 
 **Out of the round-trippable set** (deliberate; fails clean as `UnknownNodeType`):
 recording sinks (they capture an `mpsc::Sender` — runtime identity, not param-generic
-data, C19) and construction-arg builders (`LinComb` / `CostSum` / `SimBroker` /
-`Session` — structural-axis args, a C20 concern), additively addable later (#156).
+data, C19) and `SimBroker` (a scalar-typed baked value, a narrower gap than the args
+channel). `LinComb` / `CostSum` / `Session` — formerly listed here — entered the
+round-trippable set with #271's typed construction args (see the add-op `args`
+clause and the data-driven `format_version` below).
 
 ### Runs and families are built FROM blueprint-data
 
@@ -269,12 +271,13 @@ Tier-1 (additive-optional) is serde-default silent-ignore with **no** `format_ve
 bump — a new optional field defaults to prior behaviour (C1). Tier-2 (must-understand:
 a new node type, edge semantics, or structural-axis kind) **bumps** `format_version` so
 an old reader refuses cleanly (`LoadError::UnsupportedVersion` / `UnknownNodeType`).
-**Pre-ship dormancy (#61):** until the first external ship there are no out-of-repo
-readers — reader and writer change atomically in one commit — so the Tier-2 bump
-discipline is dormant and structurally-semantic additions (the `gangs` section) land as
-additive-optional fields of v1; the first ship consciously freezes v1, gangs included,
-and activates the bump discipline. The per-section required-flag scheme is deferred (no
-current Tier-2 section to validate it; recorded on #156).
+**Pre-ship dormancy (#61, ended by #271):** until the first external ship there were
+no out-of-repo readers — reader and writer changed atomically in one commit — so the
+Tier-2 bump discipline lay dormant and structurally-semantic additions (the `gangs`
+section) landed as additive-optional fields of v1. #271's construction args are the
+first exercised Tier-2 bump (data-driven, next paragraph); v1 remains the version of
+every args-free document, gangs included. The per-section required-flag scheme stays
+deferred (no per-section case yet; recorded on #156).
 
 **First data-driven bump (#271):** construction args are the first Tier-2 case whose
 version is decided PER DOCUMENT, not a single global bump. The writer emits