First commit of claude's rework in django + vanillajs fronted

apps/tools/analyzer/grouper.py

@@ -0,0 +1,60 @@
+from datetime import timedelta
+import pandas as pd
+
+OUTLIER_FACTOR = 5
+
+
+def detect_groups(df: pd.DataFrame, outlier_factor: float = OUTLIER_FACTOR,
+                  manual_splits: list | None = None,
+                  forced_splits: list | None = None) -> list:
+    """Split shots into groups.
+
+    forced_splits: when provided, ONLY these split positions are used — auto-detection
+    is bypassed entirely. Use this for user-defined groupings from the visual editor.
+
+    manual_splits: added on top of auto-detected splits (when forced_splits is None).
+    Both auto+manual mechanisms are merged and deduplicated.
+    """
+    if len(df) <= 1:
+        return [df]
+
+    def _build_groups(all_splits):
+        if not all_splits:
+            return [df]
+        groups = []
+        prev = 0
+        for pos in all_splits:
+            group = df.iloc[prev:pos]
+            if len(group) > 0:
+                groups.append(group.reset_index(drop=True))
+            prev = pos
+        last = df.iloc[prev:]
+        if len(last) > 0:
+            groups.append(last.reset_index(drop=True))
+        return groups
+
+    # Forced mode: user controls exact split positions, no auto-detection
+    if forced_splits is not None:
+        valid = sorted(s for s in forced_splits if 0 < s < len(df))
+        return _build_groups(valid)
+
+    times = df["time"]
+    diffs = times.diff().dropna()
+
+    if diffs.empty:
+        return [df]
+
+    median_gap = diffs.median()
+
+    # Auto-detect splits based on time gaps
+    auto_splits: set[int] = set()
+    if median_gap != timedelta(0):
+        threshold = outlier_factor * median_gap
+        for idx, gap in diffs.items():
+            if gap > threshold:
+                pos = df.index.get_loc(idx)
+                auto_splits.add(pos)
+
+    # Merge with manual splits (filter to valid range)
+    extra = set(manual_splits) if manual_splits else set()
+    return _build_groups(sorted(auto_splits | extra))