- upload.ts: Use fetchWithSsrFGuard directly instead of urbitFetch to
preserve full URL path when fetching external images; add release() call
- media.ts: Same fix - use fetchWithSsrFGuard for external media downloads;
add release() call to clean up resources
- channel.ts: Use urbitFetch for poke API to maintain consistent SSRF
protection (DNS pinning + redirect handling)
- upload.test.ts: Update mocks to use fetchWithSsrFGuard instead of urbitFetch
Addresses blocking issues from jalehman's review:
1. Fixed incorrect URL being fetched (validateUrbitBaseUrl was stripping path)
2. Fixed missing release() calls that could leak resources
3. Restored guarded fetch semantics for poke operations
a91d8e19b9