feat: bound climb detection by matched official climbs

Detected climbs no longer absorb an official climb's range: official climbs
matched to the route by coordinates claim their stored start/end range, and
climb detection now runs only in the free regions around them. On ride 263 a
single absorbed Cat 2 ascent is split so creating a first-half official climb
lets the second half be detected on its own.

- ride: add Range, freeRegions, and DetectClimbs(claimed); exclude claimed
  ranges so a climb never overlaps one
- official_climb: MatchClimb now bounds-matches purely by coordinates without
  needing a detected climb; extract geo.Nearest shared helper
- rideanalysis: Analyze builds claimed climbs from matched official climbs and
  detects only in free regions; render official vs unmatched climbs separately

1 files changed, 41 insertions, 2 deletions

diff --git a/ride/climb.go b/ride/climb.go
index 29a4dcf..88b9d3b 100644
--- a/ride/climb.go
+++ b/ride/climb.go
@@ -221,8 +221,47 @@ func climbsBetween(r Ride, start, end int) []Climb {
 	return climbs
 }
 
-func (ride *Ride) AllClimbs() []Climb {
-	climbs := climbsBetween(*ride, 0, ride.Len()-1)
+type Range struct {
+	Start int
+	End   int
+}
+
+func isValidClaim(claim Range, routeLen int) bool {
+	return claim.Start >= 0 && claim.End < routeLen && claim.Start < claim.End
+}
+
+// freeRegions returns the maximal sub-ranges of [rStart, rEnd] that are not
+// covered by any claimed range, after discarding claims that fall outside.
+func freeRegions(rStart, rEnd int, claimed []Range) []Range {
+	regions := make([]Range, 0, len(claimed)+1)
+	current := rStart
+	for _, claim := range claimed {
+		if !isValidClaim(claim, rEnd+1) {
+			continue
+		}
+		if claim.End < current {
+			continue
+		}
+		if claim.Start > current {
+			regions = append(regions, Range{Start: current, End: claim.Start - 1})
+		}
+		if claim.End+1 > current {
+			current = claim.End + 1
+		}
+	}
+	if current <= rEnd {
+		regions = append(regions, Range{Start: current, End: rEnd})
+	}
+	return regions
+}
+
+// returns the detected climbs of the whole ride, but never a climb that overlaps
+// a claimed range.
+func (ride *Ride) DetectClimbs(claimed []Range) []Climb {
+	climbs := make([]Climb, 0)
+	for _, region := range freeRegions(0, ride.Len()-1, claimed) {
+		climbs = append(climbs, climbsBetween(*ride, region.Start, region.End)...)
+	}
 	slices.SortFunc(climbs, climbCmpStart)
 	return climbs
 }