The Save-to-Journal flow had the browser fetch the journal with a
\`Bearer \${callbackToken}\` header. The JWT was visible in DevTools,
exfiltratable via any XSS or browser extension, and the planner's
\`loader\` shipped it down to the client as part of the page payload.
Now:
- **New action**: \`POST /api/save-to-journal\` (\`routes/api.save-to-journal.ts\`).
Body: \`{ sessionId, gpx }\`. The action loads \`callbackUrl\` +
\`callbackToken\` from \`planner.sessions\` (set at /new time when the
user came from the journal), POSTs to the journal server-to-server
with the Bearer, and forwards the response.
- **\`SaveToJournalButton\`**: drops the \`callbackUrl\` + \`callbackToken\`
props. Takes \`sessionId\` only and POSTs to the planner action.
- **\`session.\$id.tsx\` loader**: stops returning \`callbackUrl\` /
\`callbackToken\` to the client. Returns a single \`hasJournalCallback\`
boolean so the button still knows whether to render.
- **\`SessionView\`**: same prop simplification.
Trust model is unchanged: the same \`sessionId\` that grants Yjs
membership grants save authority. Knowing the URL = ability to act.
The action only adds a server-side hop so the JWT never reaches
browser JS.
Phase B (jti single-use enforcement on the journal side) follows in
a separate PR — needs a journal DB column + verifier change.
Full repo: pnpm typecheck / lint / test all green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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