docs+openspec: prior-art research (Organic Maps, Endurain, wanderer) and 15 proposals

Add docs/inspirations.md as the durable record of the 2026-07-05/06
prior-art research — per-project learnings with source paths, canonical
credit lines, and the changes each spawned — and extend the
acknowledgment lists in philosophy.md/architecture.md (Organic Maps,
Endurain, wanderer).

New OpenSpec changes (proposal/design/specs/tasks each):
- Organic Maps: elevation-profile-hardening, gpx-parser-robustness,
  hiking-time-estimate, poi-index, hiking-foot-profile
- Endurain: account-export, activity-duplicate-review,
  fit-parsing-hardening, activity-locations, self-hosting-guide,
  activity-privacy-controls
- wanderer: federation-hardening, link-share-tokens
- credits-page (user-visible acknowledgments)

Updated in-flight changes with wanderer prior-art sections:
route-federation, route-discovery.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

openspec/changes/hiking-time-estimate/proposal.md

@@ -0,0 +1,29 @@
+## Why
+
+The planner shows distance and ascent for a planned route but no time estimate, even though "how long will this take?" is the first question a hiker asks of a plan — and even though BRouter already returns elevation-tagged geometry that makes a good estimate cheap to compute. Tobler's hiking function (speed as a function of slope, the model Organic Maps uses for pedestrian ETA) turns the existing route geometry into a credible walking-time estimate with a small pure function. Bonus: the `multi-day-routes` spec already requires per-day "estimated duration", which was never implemented — this change closes that drift.
+
+## What Changes
+
+- New pure function in `@trails-cool/gpx`: Tobler-based walking time over a sequence of points with elevation (`speed = 6·e^(−3.5·|slope+0.05|)` km/h per segment, flat-ground fallback when elevation is missing).
+- The planner sidebar shows **estimated walking time** alongside distance and ascent when the routing profile is the foot profile (`trekking`, labeled "Hiking" in the UI). Cycling/car profiles show no estimate (out of scope for now).
+- `computeDays` gains an opt-in per-day `estimatedTimeSec` so the multi-day day breakdown shows a time per day (planner only; journal's `computeDays` call is unaffected).
+- Estimates are labeled as walking time without breaks (signpost convention), localized in English and German.
+- Not in scope: cycling time estimates (BRouter's `total-time` is already summed in `EnrichedRoute.totalTime` and could be surfaced later), journal route detail display, rest-break padding (DIN 33466-style), and any change to routing itself.
+
+## Capabilities
+
+### New Capabilities
+- `hiking-time-estimate`: Tobler-based walking-time estimation for planned routes — the model, where it appears (whole-route stats, per-day stats), when it applies (foot profile), and its fallback behavior without elevation data.
+
+### Modified Capabilities
+
+<!-- none — multi-day-routes already requires per-day estimated duration (currently unimplemented); this change fulfills that requirement rather than changing it. The new capability spec covers the estimation model and display details. -->
+
+## Impact
+
+- `packages/gpx/src/hiking-time.ts` (new) + tests — the Tobler function and a cumulative variant for day splits.
+- `packages/gpx/src/compute-days.ts` — optional `estimatedTimeSec` on `DayStage` behind an opt-in flag; existing callers unchanged.
+- `apps/planner/app/lib/use-routing.ts` — compute `estimatedTimeSec` into route stats when the profile is `trekking`, from the enriched route's elevation-tagged coordinates.
+- `apps/planner/app/components/WaypointSidebar.tsx` + `DayBreakdown.tsx` — display whole-route and per-day time.
+- `packages/i18n` — new planner strings (en + de).
+- No API, schema, or BRouter changes.