- Top-level dispatch switches on fqSlot (parentSlot.slot) so dotted top-level
slots (`stage.cone`, `stage.voice`, `articles.<subtype>`) are matched.
- `stage_voice` -> `stage.cone` (new, one per score) + `stage.voice` (list).
- `article` -> `articles.<subtype>` (subtype stored on the article entry;
first observed subtype is `defaults`).
- New `tuning.frequency_factors` child captured as `{ label, factors }`.
- buildModel un-nests preamble siblings that sompyler emits at depth 01
under `00 tuning` via `with deeper_level("articles")` / `deeper_level("stage")`.
Only `tuning`'s children are flattened; `instrument`'s implicit containers
(`character`, `VOLUMES`, `TIMBRE`, `FM`, `AM`) are left untouched.
- Fixture test extended with 18 preamble assertions (172 total now pass).
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