iter cma.3: live Qwen3-Coder-Next run + DESIGN.md §Decision-6 empirical addendum + milestone close

Milestone "Cross-model authoring-form test" closed. Live IONOS run
against Qwen/Qwen3-Coder-Next executed at temperature=0, max-turns=5,
token-budget=500000. Raw dataset under runs/2026-05-12-df7531/:
RUN_STATUS=ok, scores.csv with 8 rows (4 tasks × 2 cohorts),
summary.md, plus 156 per-turn raw artefacts (request/response/program/
stderr/stdout) preserved for any future analysis.

Headline numbers:
- AILX cohort: 2/4 green, 1/4 first-attempt, ~95k prompt + ~2.6k completion
- JSON cohort: 1/4 green, 0/4 first-attempt, ~192k prompt + ~15k completion
- Only first-attempt success was AILX on t3_main_prints (~5 lines of
  tagged s-expr vs ~23 lines of structured JSON for the JSON cohort's
  turn-1 attempt that needed correction).
- Per spec, single subject + single deterministic run = data point,
  not verdict.

DESIGN.md §"Decision 6: authoring surface" gains an "Empirical
addendum (2026-05-12)" subsection: 6-row metric table, illustrative
t3 contrast, explicit single-subject scope note pointing at the
roadmap follow-up entry for multi-subject expansion.

Roadmap: P2 entry "Cross-model authoring-form test" removed (this
journal is the convention's one-line mirror); P3 entry
"Multi-subject expansion (cross-model authoring-form follow-up)"
added with the run dir named as baseline.

Milestone artefacts span three iters (cma.1 master mini-spec +
renderer; cma.2 harness + tasks + reference solutions; cma.3 this
live run + DESIGN.md addendum + close).

docs/journals/INDEX.md

@@ -22,3 +22,4 @@
 - 2026-05-12 — iter boss: `/boss` skill — autonomous-mode discipline (Direction freedom, Notifications, WhatsNew procedure) extracted from CLAUDE.md into a user-invoked skill → 2026-05-12-iter-boss.md
 - 2026-05-12 — iter cma.1: master mini-spec + render binary for cross-model authoring experiment (13 fixtures cover 34/34 AST variants, 4 test gates green, rendered/{json,ailx}.md checked in; out-of-workspace nested crate) → 2026-05-12-iter-cma.1.md
 - 2026-05-12 — iter cma.2: harness binary + 4 tasks + reference solutions + 4 integration tests (six modules, real-pipeline preflight via verify_references, 13/13 tests green; pipeline.rs renames program file to module-name for ail check) → 2026-05-12-iter-cma.2.md
+- 2026-05-12 — iter cma.3: live Qwen3-Coder-Next run + DESIGN.md §Decision-6 empirical addendum + roadmap close (AILX 2/4 green vs JSON 1/4; ~98k vs ~207k tokens; single-subject scope explicit, multi-subject expansion queued as P3) → 2026-05-12-iter-cma.3.md