Use garden session sources for GitP publication

[codekiln]

GitP episode text and linked assets repeat across production notes, JSON handoffs, and Gitpa records. Use four dated session pages as the episode sources, with recording, artwork, preset, and MIDI asset pages under their existing names. Gitpa mirrors these source bodies and owns publication identity and listener presentation.

Replace the JSON handoff generator and its duplicate metadata instructions with the session/asset workflow. Document source preparation and anonymous media verification, and bring the saved October 5 plans and journal records into this source branch. All asset URLs use the public S3 endpoint recorded in the garden configuration, retaining their page-derived filenames in the public garden bucket.

Validation:

• Every session embed resolves to a source page, and all asset URL filenames match their page names.
• Anonymous HEAD requests returned HTTP 200 for all 14 assets, with audio/mpeg for MP3 and image/gif for artwork. All four MP3 range requests returned HTTP 206 with Content-Range.
• The original f005 download host failed local DNS and browser media loading. The official S3 endpoint succeeds anonymously without a DNS override; all MP3 range requests return HTTP 206. Browser artwork loads at the new URL. Embedded playback is verified through the paired publication preview.
• Added wikilinks resolve, protected tags and existing block IDs remain unchanged, and commit secret/identity checks pass.

Paired listener presentation and homepage query: Gitpa #12. Merge these garden sources before publishing Gitpa so its proxy source links resolve on main.

Reusable proxy contracts and portable tasks are owned separately by garden #182. Asset automation is delivered separately in DVC tasks #179 and cached B2 uploads #180.

Closes #181.