Extract climb detection into a dedicated climb package

Move climb detection, slope, and Cotacol scoring out of ride into a new
climb package that operates on a geometry-only Route (distances, elevations,
coords). Ride embeds climb.Route and keeps its timing and telemetry columns.

- climb.Detect returns []DetectedClimb (Climb + ride-absolute Start).
- Climb owns its sliced geometry; indices are local, with Start reported at
  the detection boundary for absolute position.
- Detected bounds use core.Interval; freeRegions claim suppression fixed.
- ride no longer builds slices: ClimbFromDist/ClimbFromIndexes/climbFrom and
  ride.Climb/Interval/Range are removed; rideanalysis, mountain_pass MatchClimb,
  and web views are rewired to climb types.
- New internal/routetest builds climb.Route from the ride DSL; ridetest reuses
  it and adds timestamps and telemetry.
- Tests moved to climb (synthetic detection and difficulty) and kept in ride
  for GPX-example integration; ride.comparison detection coverage retained.
- mountain_pass.nearestCrossing now reuses geo.Nearest.

1 files changed, 87 insertions, 0 deletions

diff --git a/climb/climb.go b/climb/climb.go
new file mode 100644
index 0000000..2d764dd
--- /dev/null
+++ b/climb/climb.go
@@ -0,0 +1,87 @@
+package climb
+
+import (
+	"fmt"
+	"math"
+)
+
+const (
+	ClimbDistanceMinimum  = 500
+	ClimbSlopeMinimum     = 0.035
+	detectionMinimumScore = 35
+)
+
+type Category int
+
+const (
+	CategoryNo Category = iota
+	CategoryFour
+	CategoryThree
+	CategoryTwo
+	CategoryOne
+	CategoryHC
+)
+
+type categoryInfo struct {
+	label    string
+	minScore float64
+}
+
+var categories = map[Category]categoryInfo{
+	CategoryNo:    {label: "NO", minScore: math.Inf(-1)},
+	CategoryFour:  {label: "Cat 4", minScore: 35},
+	CategoryThree: {label: "Cat 3", minScore: 80},
+	CategoryTwo:   {label: "Cat 2", minScore: 180},
+	CategoryOne:   {label: "Cat 1", minScore: 250},
+	CategoryHC:    {label: "HC", minScore: 600},
+}
+
+func (c Category) String() string {
+	return categories[c].label
+}
+
+func CategoryOf(cotacol float64) Category {
+	best := CategoryNo
+	bestMin := math.Inf(-1)
+	found := false
+	for category, info := range categories {
+		if cotacol >= info.minScore && (!found || info.minScore > bestMin) {
+			best = category
+			bestMin = info.minScore
+			found = true
+		}
+	}
+	if !found {
+		// NaN reaches no floor; preserve the original switch default (HC).
+		return CategoryHC
+	}
+	return best
+}
+
+type Climb struct {
+	Route
+}
+
+func (climb Climb) String() string {
+	cotacol := climb.DifficultyScore()
+	return fmt.Sprintf("%.1fkm at %.1f%% (%d pts - %s)", climb.Distances[len(climb.Distances)-1]/1000, Slope(climb.Distances, climb.Elevations)*100, int(cotacol), CategoryOf(cotacol))
+}
+
+func (climb Climb) DifficultyScore() float64 {
+	return Cotacol(climb.Distances, climb.Elevations)
+}
+
+func (climb Climb) Top() (int, float64) {
+	top := 0
+	for i := 1; i < len(climb.Elevations); i++ {
+		if climb.Elevations[i] > climb.Elevations[top] {
+			top = i
+		}
+	}
+	return top, climb.Elevations[top]
+}
+
+func Slope(distances, elevations []float64) float64 {
+	end := len(distances) - 1
+	return (elevations[end] - elevations[0]) / (distances[end] - distances[0])
+}