iter design-md-rolesplit.1 (DONE 9/9): DESIGN.md -> design/ ledger role-split

The 3020-line docs/DESIGN.md is replaced by the design/ ledger:
design/INDEX.md (sole addressable spine, typed Contracts+Models tables,
polymorphic links — prose file OR authoritative source //!), 14
design/contracts/*.md test-linked invariants + 3 source-link-only
contracts (mangling/env-construction/qualified-xref, no prose file —
code is SoT), 5 design/models/*.md whitepapers, and
docs/journals/2026-05-19-design-decision-records.md (the
relitigation-guard archive — every why/rejected/does-not-do/rollback/
empirical ### moved out at ###-granularity). Clean cut: git rm
docs/DESIGN.md, no stub.

RED-first crates/ailang-core/tests/design_index_pin.rs — the 4-clause
anti-regrowth spine (DESIGN.md-gone / every-INDEX-link-resolves /
every-contract-names-a-resolvable-ratifier /
contracts-carry-no-decision-record-prose) — demonstrably RED before,
GREEN after. Build-atomic by task ordering: design_schema_drift.rs's
include_str! (the only compile-time consumer) retargeted to
design/contracts/data-model.md BEFORE the deletion; its
## Data model/## Pipeline slicer dropped (a simplification the split
enables). 2 NoInstance diagnostics + 2 lockstep E2Es retargeted to
design/contracts/{float-semantics,typeclasses}.md. ~12 agent reading
lists + 5 SKILL bodies + CLAUDE.md + skills/README.md + ~25
code/C/.ail/spec comment xrefs retargeted; OQ7 dangling 'Iter 13b'
cite deleted (no forward target — a pointer would be fiction).
honesty-rule.md rewritten so the rule names the new home
(rationale->journals), resolving the recon-found internal
contradiction; the two docs_honesty_pin.rs:70,72 pinned phrases kept
verbatim+contiguous.

Boss-verified independently: cargo test --workspace 646 passed /
0 failed; design_index_pin 4/4; acceptance grep CLEAN of live
DESIGN.md refs (residuals = only the spec-mandated clause-4
deletion-enforcer). 2 DONE_WITH_CONCERNS routed to the mandatory
milestone-close audit: (a) str-abi.md:23 '(iter str-concat,
2026-05-13)' provenance stamp trips advisory architect_sweeps Sweep-1
— Boss-confirmed byte-identical to DESIGN.md@deeffb1:2062-2065, a
faithfully-migrated PRE-EXISTING anchor (regexes verbatim, only path
retargeted), NOT split-introduced — RATIFY-or-tidy at audit; (b) a
now stale-direction intra-prose 'see Str ABI below' cross-ref in
float-semantics.md — audit-adjudication candidate. Plan defect noted:
Task 9 Step 4's verbatim acceptance grep used a ^./ anchor not
matching the system's grep -rIn output; substance re-verified CLEAN.

Spec grounding-check PASS x2. Journals INDEX + decision-records
pointer appended (Boss-only).

runtime/rc.c

@@ -38,9 +38,9 @@
  * `GC_malloc`-returned pointer; it stores the ADT tag at offset 0,
  * fields from offset 8, env-cells from offset 0 in lambda envs, etc.
  *
- * FROZEN ABI for the embedding boundary — see DESIGN.md §"Embedding
- * ABI" > "Frozen value layout". A boundary-crossing single-ctor
- * scalar record's box offsets MUST NOT move.
+ * FROZEN ABI for the embedding boundary — see
+ * design/contracts/frozen-value-layout.md. A boundary-crossing
+ * single-ctor scalar record's box offsets MUST NOT move.
  *
  * Threading: the per-object refcount header ops and the per-ctx RC
  * counters are non-atomic by design — a box never crosses a thread

runtime/str.c

@@ -169,7 +169,7 @@ char *ailang_bool_to_str(bool b) {
  * the trailing NUL. Works uniformly on static-Str and heap-Str
  * inputs because the consumer ABI (i64 len at offset 0, bytes
  * starting at offset 8, NUL at offset 8 + len) is identical
- * between realisations (see DESIGN.md §"Str ABI"); the rc_header at
+ * between realisations (see design/contracts/str-abi.md); the rc_header at
  * offset -8 — present only on heap-Str — is never consulted.
  *
  * Used by `show__Str` (parent spec milestone 24): converts a
@@ -195,7 +195,7 @@ char *ailang_str_clone(const char *src) {
  * memcpys both payloads in order, NUL-terminates, returns the new
  * payload pointer. Like `str_clone`, this works uniformly on static-
  * Str and heap-Str inputs because the consumer ABI is identical
- * between realisations (see DESIGN.md §"Heap-Str primitives").
+ * between realisations (see design/contracts/str-abi.md).
  *
  * Used by Show bodies that want labelled output (e.g.
  * `"Item " ++ int_to_str n`) and by any caller that needs to