feat: professional reggaeton production engine — 7 SDD changes, 302 tests

- section-energy: track activity matrix + volume/velocity multipliers per section
- smart-chords: ChordEngine with voice leading, inversions, 4 emotion modes
- hook-melody: melody engine with hook/stabs/smooth styles, call-and-response
- mix-calibration: Calibrator module (LUFS volumes, HPF/LPF, stereo, sends, master)
- transitions-fx: FX track with risers/impacts/sweeps at section boundaries
- sidechain: MIDI CC11 bass ducking on kick hits via DrumLoopAnalyzer
- presets-pack: role-aware plugin presets (Serum/Decapitator/Omnisphere per role)

Full SDD pipeline (propose→spec→design→tasks→apply→verify) for all 7 changes.
302/302 tests passing.

.sdd/changes/section-energy/tasks.md

@@ -0,0 +1,32 @@
+# Tasks: Section Energy Curve
+
+## Phase 1: Schema + Foundation
+
+- [x] 1.1 Add `vol_mult: float = 1.0` field to `ClipDef` in `src/core/schema.py`
+- [x] 1.2 Add `TRACK_ACTIVITY` dict and `_section_active()` helper to `scripts/compose.py`
+- [x] 1.3 Add `SECTION_MULTIPLIERS` dict and update `build_section_structure()` to set `velocity_mult` and `vol_mult` per section type
+- [x] 1.4 Rename `build` → `pre-chorus` in `SECTIONS` and `DRUMLOOP_ASSIGNMENTS` in `scripts/compose.py`
+
+## Phase 2: Builder Refactor
+
+- [x] 2.1 Refactor `build_drumloop_track()` — use `_section_active()` instead of `DRUMLOOP_ASSIGNMENTS` dict lookup
+- [x] 2.2 Refactor `build_perc_track()` — replace `if section.name in (...)` with `_section_active()`
+- [x] 2.3 Refactor `build_bass_track()` — replace `section.energy` with `section.velocity_mult` for velocity calc
+- [x] 2.4 Refactor `build_chords_track()` — use `_section_active()` for section check, `velocity_mult` for velocity
+- [x] 2.5 Refactor `build_lead_track()` — use `_section_active()` for section check, `velocity_mult` for velocity
+- [x] 2.6 Refactor `build_clap_track()` — use `_section_active()` instead of `section.name.startswith(...)`
+- [x] 2.7 Refactor `build_pad_track()` — use `_section_active()` for section check, `velocity_mult` for velocity
+
+## Phase 3: RPPBuilder D_VOL Emission
+
+- [x] 3.1 Update `_build_clip()` in `src/reaper_builder/__init__.py` to emit `D_VOL` when `clip.vol_mult != 1.0` and clip is audio
+- [x] 3.2 Update `_build_midi_source()` to scale notes by `clip.vol_mult` (post-processing fallback)
+
+## Phase 4: Tests
+
+- [x] 4.1 Add `test_build_section_structure_sets_multipliers` to `tests/test_section_builder.py` — verify per-section velocity_mult/vol_mult
+- [x] 4.2 Add `test_section_active_helper` — edge cases: unknown section, unknown role, all known combos
+- [x] 4.3 Add `test_clipdef_vol_mult_default` to `tests/test_core_schema.py`
+- [x] 4.4 Add `test_dvol_emission` to `tests/test_reaper_builder.py` — audio clip vol_mult≠1.0 emits D_VOL, default vol_mult=1.0 does not
+- [x] 4.5 Update `test_compose_integration.py` — verify sparse intro (no bass/chords/lead) vs dense chorus, section rename
+- [x] 4.6 Run full test suite (167 tests) — 161 pass, 6 pre-existing failures in test_chords.py (unrelated)