VAM: drop duration curve, show avg climbing VAM in Nerd Corner

Remove the per-duration VAM curve everywhere (metrics, summaries, detail
JSON, athlete.json, VamChart.svelte, AthleteView VAM tab). Keep only
climbing_vam_mh per activity. Add it to activity summaries so NerdCorner
can plot average climbing VAM per week/month year-over-year alongside
distance/elevation/time. Add --backfill-vam-summary flag to copy the
field from existing detail JSONs into index.json without re-extracting.

bincio/render/cli.py

@@ -116,7 +116,7 @@ def _rebuild_athlete_json(data: Path, handle: str | None = None) -> None:
     from bincio.render.merge import parse_sidecar, _apply_sidecar_summary
 
     targets = [data / handle] if handle else _user_dirs(data)
-    _COMPUTED = {"bas_version", "generated_at", "power_curve", "vam_curve", "records", "best_climbs"}
+    _COMPUTED = {"bas_version", "generated_at", "power_curve", "records", "best_climbs"}
     for user_dir in targets:
         index_path = user_dir / "index.json"
         if not index_path.exists():
@@ -377,10 +377,12 @@ def _link_data(site: Path, data: Path) -> None:
     console.print(f"Linked data: [cyan]{target}[/cyan] → [cyan]{public_data}[/cyan]")
 
 
-def _recompute_vam(data: Path, handle: str | None = None) -> None:
-    """Recompute climbing_vam_mh and vam_curve for all activities from stored timeseries."""
+def _backfill_vam_summary(data: Path, handle: str | None = None) -> None:
+    """Copy climbing_vam_mh from detail JSONs into index.json summaries.
+
+    Needed once after the vam_curve→climbing_vam_mh-in-summary migration.
+    """
     import json
-    from bincio.extract.metrics import compute_vam_from_timeseries
 
     targets = [data / handle] if handle else _user_dirs(data)
     for user_dir in targets:
@@ -394,31 +396,18 @@ def _recompute_vam(data: Path, handle: str | None = None) -> None:
             continue
 
         updated = 0
-        for act_path in acts_dir.glob("*.json"):
-            if act_path.stem.endswith((".timeseries", ".geojson")):
-                continue
-            ts_path = acts_dir / f"{act_path.stem}.timeseries.json"
-            if not ts_path.exists():
+        for s in index_data.get("activities", []):
+            if "climbing_vam_mh" in s:
+                continue  # already backfilled
+            act_path = acts_dir / f"{s['id']}.json"
+            if not act_path.exists():
                 continue
             try:
                 detail = json.loads(act_path.read_text(encoding="utf-8"))
-                sport = detail.get("sport", "other")
-                ts = json.loads(ts_path.read_text(encoding="utf-8"))
-                new_vam, new_curve = compute_vam_from_timeseries(ts, sport)
-                if (new_vam == detail.get("climbing_vam_mh")
-                        and new_curve == detail.get("vam_curve")):
-                    continue
-                detail["climbing_vam_mh"] = new_vam
-                detail["vam_curve"] = new_curve
-                act_path.write_text(
-                    json.dumps(detail, indent=2, ensure_ascii=False), encoding="utf-8"
-                )
-                act_id = act_path.stem
-                for s in index_data.get("activities", []):
-                    if s.get("id") == act_id:
-                        s["vam_curve"] = new_curve
-                        break
-                updated += 1
+                vam = detail.get("climbing_vam_mh")
+                if vam is not None:
+                    s["climbing_vam_mh"] = vam
+                    updated += 1
             except Exception:
                 pass
 
@@ -426,7 +415,7 @@ def _recompute_vam(data: Path, handle: str | None = None) -> None:
             index_path.write_text(
                 json.dumps(index_data, indent=2, ensure_ascii=False), encoding="utf-8"
             )
-        console.print(f"  [cyan]{user_dir.name}[/cyan]: {updated} activity(ies) updated")
+        console.print(f"  [cyan]{user_dir.name}[/cyan]: {updated} summary(ies) updated")
 
 
 @click.command()
@@ -452,9 +441,9 @@ def _recompute_vam(data: Path, handle: str | None = None) -> None:
 @click.option("--recompute-elevation", "recompute_elevation", is_flag=True,
               help="Recompute elevation_gain_m/loss_m for all activities from stored timeseries "
                    "(run once after upgrading the dropout-skip fix).")
-@click.option("--recompute-vam", "recompute_vam", is_flag=True,
-              help="Recompute climbing_vam_mh and vam_curve for all activities from stored "
-                   "timeseries (run once after adding VAM support).")
+@click.option("--backfill-vam-summary", "backfill_vam_summary", is_flag=True,
+              help="Copy climbing_vam_mh from detail JSONs into index.json summaries "
+                   "(run once after the VAM curve → summary migration).")
 def render(
     config_path: Optional[str],
     data_dir: Optional[str],
@@ -466,7 +455,7 @@ def render(
     no_build: bool,
     recompute_climbs: bool,
     recompute_elevation: bool,
-    recompute_vam: bool,
+    backfill_vam_summary: bool,
 ) -> None:
     """Build (or serve) the BincioActivity static site from a BAS data store."""
 
@@ -484,9 +473,9 @@ def render(
         console.print("Recomputing elevation gain/loss from timeseries…")
         _recompute_elevation(data, handle=handle)
 
-    if recompute_vam:
-        console.print("Recomputing VAM from timeseries…")
-        _recompute_vam(data, handle=handle)
+    if backfill_vam_summary:
+        console.print("Backfilling climbing_vam_mh into summaries…")
+        _backfill_vam_summary(data, handle=handle)
 
     _merge_edits(data, handle=handle)
     _rebuild_athlete_json(data, handle=handle)