openspec: propose journal route/activity detail catch-up changes

Three OpenSpec proposals to bring the journal's route/activity detail and feed
closer to best-in-class outdoor apps, in the order we'll implement them:

- activity-sport-type: nullable sport enum on activities (hike/walk/run/
  ride/gravel/mtb/ski/other), set on create or normalized on import,
  shown as a badge + feed verb, federated as a Note PropertyValue.
- activity-stats: one reusable StatRow + canonical metric set, sport-aware
  avg pace/speed, moving-vs-elapsed time. Derive-only, no schema change.
- journal-elevation-profile: elevation profile chart + chart<->map
  "active distance" hover/click sync on the read-only detail pages.

All three validate with `openspec validate --strict`. Specs only; no code.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

openspec/changes/journal-elevation-profile/proposal.md

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+## Why
+
+The Journal's route and activity detail pages show elevation only as two numbers
+(gain/loss) even though the full elevation series is already parsed from the
+GPX. Both Komoot and Strava treat the elevation profile as the second hero
+object after the map, and the interaction that makes a route feel
+"inspectable" — hovering the profile to move a marker on the map, and
+vice-versa — is the single most satisfying detail-page feature. We already have
+this interaction specced and built on the **Planner**
+(`elevation-map-interaction`); this change ports a read-only version to the
+Journal detail pages.
+
+## What Changes
+
+- Render an elevation profile chart on the route detail and activity detail
+  pages: a gradient-filled area chart (x = distance, y = elevation) with a
+  summary strip (ascent · descent · highest · lowest).
+- Add a shared "active distance" interaction: hovering the chart highlights the
+  corresponding point on the Leaflet map (a marker), and hovering the route line
+  highlights the corresponding position on the chart. Both stay in sync.
+- Clicking a point on the chart centers the map on that location (read-only —
+  no editing, unlike the Planner).
+- Degrade gracefully: when the GPX has no usable elevation series, the chart is
+  omitted (the gain/loss numbers remain).
+
+## Capabilities
+
+### New Capabilities
+
+- `journal-elevation-profile`: the elevation profile chart and the
+  chart↔map "active distance" interaction on the Journal's read-only route and
+  activity detail pages.
+
+### Modified Capabilities
+
+<!-- None. `elevation-map-interaction` describes the Planner's editing-context
+     interaction; this is a separate read-only capability on the Journal detail
+     pages. They share the "active distance" concept but not the same surface or
+     requirements. -->
+
+## Impact
+
+- **Journal app**: a new `ElevationProfile` chart component, a shared
+  "active distance" state lifted over the detail page's map + chart, and wiring
+  in `routes.$id.tsx` and `activities.$id.tsx`. Loaders expose the elevation
+  series (derived from existing `gpx`).
+- **Packages**: reuse `@trails-cool/gpx` for the elevation/distance series and
+  `@trails-cool/map-core` for the elevation color scale; no new dependency.
+- **i18n**: `journal.elevation.*` keys (en + de) for the summary labels.
+- No schema or wire-contract change.