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>

docs/architecture.md

@@ -22,7 +22,8 @@ These principles inform key architectural and product decisions:
   visualizations and tools around their data.
 - **Open source (MIT)**: The code is MIT licensed — both because of the
   commitment to the open web, and out of respect for the open-source projects
-  that inspire trails.cool (BRouter, bikerouter.de, brouter-web).
+  that inspire trails.cool (BRouter, bikerouter.de, brouter-web, Organic Maps,
+  Endurain, wanderer).
 - **AI-assisted development**: AI (Claude Code) and spec-driven development
   (OpenSpec) are core to how this project is built. Human contributions are
   very welcome. This is also an experiment in how far AI-assisted development