fix(review): load private GitHub PR images and videos

[rynfar]

Private GitHub screenshots and recordings in PR descriptions/comments currently load without credentials and can return 404. Route supported GitHub media through short-lived signed Pylon asset URLs, using the active GitHub CLI account on the repository's environment. Images preserve authored sizing, original links, retries and older-server public fallback; videos stream range responses for seeking.

Adopts maria / maria-rcks's upstream work in 32e8b2584556c0c55ce0d1d8f72b506cb771d60d (#11706), retaining original authorship and coauthor credit. Pylon adaptations preserve local path restrictions, context rendering and provider behavior. Direct adversarial review removed the process-global token cache so account changes/logout apply to the next request, restricted redirects to GitHub media/CDN hosts, stripped credentials on signed CDN hops, and kept credential-bearing failures out of logs. GitHub Enterprise media is unsupported; no account-routing feature imported.

Validation: 37 AssetAccess tests, 11 HTTP transport regressions (including malformed/unsafe redirects, account credential handling, range streaming, MIME and SVG sandbox), and 100 markdown regressions pass. Scoped server, web, contracts, client-runtime and mobile typechecks passed; scoped lint passes with existing warnings. Account switch/login/logout regression is in AssetAccess tests. Browser screenshots and playback recording are attached; real private-repository delivery is covered by controlled transport tests, not claimed as a live private-repository check.

Rebased onto merged #626: 64 integrated asset/transport/CLI regressions and the server typecheck pass; the conflict preserves the merged quota guards and environment forwarding.

Part of #625. No release or installation.

Implemented and adversarially self-reviewed with Codex (GPT-6), without delegation at the maintainer's request.

[vercel]

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Project	Deployment	Actions	Updated
pylon-marketing	Ready	Preview	Sep 18, 2026 3:26pm UTC

[rynfar]

Browser verification on 832493b: six public GitHub fixture images loaded through signed Pylon asset URLs; expanded image preview and video playback worked. The recording shows six seconds of continuous proxied playback. Private access, login/account switch/logout, unsafe redirects, credential stripping and range responses are covered by controlled transport regressions; this is not a claim of live private-repository testing.

Attachments: baseline, updated image preview, updated video, playback recording.

media-playback.mp4

Rebased onto merged #626 afterward; media UI unchanged. The CLI conflict retains #626’s environment forwarding and quota guards. Final-head CI and integrated media/CLI regressions are required before merge.

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	14.0 KiB	13.9 KiB	−56 B (−0.4%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.2 KiB	7.2 KiB	−4 B (−0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.7 KiB	6.7 KiB	−52 B (−0.8%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	−44 B (−0.1%)	66.4 KiB	✅
Codex	Live turn messages	9	8	−1 (−11.1%)	21	✅
Claude	Total thread wire	14.0 KiB	13.9 KiB	−63 B (−0.4%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.2 KiB	7.2 KiB	+4 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.8 KiB	6.7 KiB	−67 B (−1.0%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.9 KiB	58.8 KiB	−44 B (−0.1%)	66.4 KiB	✅
Claude	Live turn messages	9	8	−1 (−11.1%)	21	✅

Baseline: 6d8ebeb · PR result: 9bcbf71 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 115.7 KiB
• Claude decoded thread snapshot: 116.4 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.