feat: pattern-based generators from real track analysis, RPP structure fixes, randomization

- Reverse-engineer drum patterns from 2 real reggaeton tracks with librosa
- Create patterns.py with extracted frequency data (kick/snare/hihat positions)
- Rewrite rhythm.py with pattern-bank generators (dembow, dense, trapico, offbeat)
- Rewrite melodic.py with section-aware generators and humanization
- Add weighted random sample selection in SampleSelector (top-5 pool)
- Add generate_structure() with randomized templates and energy variance
- Fix RPP structure: TEMPO arity (3→4 args), string quoting for empty strings
- Rewrite quick_drumloop_test.py with correct REAPER ground truth format
- Add scripts/analyze_examples.py for reverse engineering audio tracks
- Add --seed argument for reproducible generation
- 72 tests passing

src/reaper_builder/__init__.py

@@ -51,13 +51,13 @@ _PROJECT_HEADER: list[list[str] | Element] = [
     ["SMPTESYNC", "0", "30", "100", "40", "1000", "300", "0", "0", "1", "0", "0"],
     ["LOOP", "0"],
     ["LOOPGRAN", "0", "4"],
-    ["RECORD_PATH", '"Media"', '""'],
+    ["RECORD_PATH", "Media", ""],
     Element("RECORD_CFG", [], children=["ZXZhdxgAAQ=="]),
     [],
     Element("APPLYFX_CFG", [], children=[]),
     [],
-    ["RENDER_FILE", '""'],
-    ["RENDER_PATTERN", '""'],
+    ["RENDER_FILE", ""],
+    ["RENDER_PATTERN", ""],
     ["RENDER_FMT", "0", "2", "0"],
     ["RENDER_1X", "0"],
     ["RENDER_RANGE", "1", "0", "0", "0", "1000"],
@@ -181,8 +181,10 @@ _FXCHAIN_FOOTER: list[list[str]] = [
 # ---------------------------------------------------------------------------
 
 def _make_guid() -> str:
-    """Generate a random REAPER GUID string."""
-    return str(uuid.uuid4()).upper()
+    """Generate a random REAPER GUID string using random module (seedable)."""
+    # Use random module directly so seeding works
+    import random
+    return str(uuid.UUID(bytes=bytes(random.getrandbits(8) for _ in range(16)), version=4)).upper()
 
 
 def vst3_element(display_name: str, filename: str, uid_guid: str = "", preset_data: list[str] | None = None) -> Element:
@@ -233,8 +235,17 @@ class RPPBuilder:
         builder.write("output.rpp")
     """
 
-    def __init__(self, song: SongDefinition) -> None:
+    def __init__(self, song: SongDefinition, seed: int | None = None) -> None:
         self.song = song
+        self._seed = seed
+        if seed is not None:
+            import random
+            random.seed(seed)
+
+    def _make_seeded_guid(self) -> str:
+        """Generate a random REAPER GUID string. Uses seed if provided to RPPBuilder."""
+        import random
+        return str(uuid.UUID(bytes=bytes(random.getrandbits(8) for _ in range(16)), version=4)).upper()
 
     def write(self, path: str | Path) -> None:
         """Serialize the project to a .rpp file at *path*.
@@ -255,7 +266,9 @@ class RPPBuilder:
         m = self.song.meta
 
         # Project root — version from test_vst3.rpp line 1
-        root = Element("REAPER_PROJECT", ["0.1", "7.65/win64", str(int(uuid.uuid4().time)), "0"])
+        # Use random to make it seedable for reproducible output
+        import random
+        root = Element("REAPER_PROJECT", ["0.1", "7.65/win64", str(random.getrandbits(64)), "0"])
 
         # Add all static project header lines
         for line in _PROJECT_HEADER:
@@ -263,10 +276,11 @@ class RPPBuilder:
                 root.append(line)
 
         # TEMPO is injected dynamically (overrides static header)
-        root.append(["TEMPO", str(m.bpm), str(m.time_sig_num), str(m.time_sig_den)])
+        # REAPER format: TEMPO bpm time_sig_num time_sig_den flag (flag=0 for standard)
+        root.append(["TEMPO", str(m.bpm), str(m.time_sig_num), str(m.time_sig_den), "0"])
 
         # Master track
-        master_guid = _make_guid()
+        master_guid = self._make_seeded_guid()
         master = Element("TRACK", [master_guid])
         master.append(['NAME', "master"])
         master.append(["VOLPAN", "1.0", "0", "-1", "-1", "1"])
@@ -285,7 +299,7 @@ class RPPBuilder:
             if line:
                 footer_copy = [v for v in line]
                 if footer_copy[0] == "FXID":
-                    footer_copy[1] = f"{{{_make_guid()}}}"
+                    footer_copy[1] = f"{{{self._make_seeded_guid()}}}"
                 master_fxchain.append(footer_copy)
         master.append(master_fxchain)
         root.append(master)
@@ -298,7 +312,7 @@ class RPPBuilder:
 
     def _build_track(self, track: TrackDef) -> Element:
         """Build a TRACK Element with all default attributes from test_vst3.rpp."""
-        track_guid = _make_guid()
+        track_guid = self._make_seeded_guid()
         track_elem = Element("TRACK", [f"{{{track_guid}}}"])
         track_elem.append(["NAME", track.name])
 
@@ -332,7 +346,7 @@ class RPPBuilder:
                 fxchain.append([v for v in line])
             for plugin in track.plugins:
                 fxchain.append(self._build_plugin(plugin))
-            fxid_guid = _make_guid()
+            fxid_guid = self._make_seeded_guid()
             fxchain.append(["PRESETNAME", "Program 1"])
             fxchain.append(["FLOATPOS", "0", "0", "0", "0"])
             fxchain.append(["FXID", f"{{{fxid_guid}}}"])