GPX data was being encoded in URL params, causing HTTP 431 (Request
Header Fields Too Large). Now the Journal creates a Planner session
via POST to /api/sessions with GPX in the request body, then
redirects to the session URL (154 chars vs 100KB+).
Also moved edit-in-planner logic to dedicated API route for proper
JSON response handling.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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