fix(ci): deploy the relay only when the relay changes

[rynfar]

The production relay deploy ran on every push to pylon, whatever the push changed. It has also failed on every run since the Alchemy upgrade (last success 2026-09-26), because its bootstrap step calls alchemy cloudflare bootstrap and Alchemy moved that to alchemy provider cloudflare bootstrap.

Fix

• The push trigger is limited to infra/relay/**, excluding Markdown. Manual dispatch is unchanged.
• The bootstrap step uses the new command. alchemy provider cloudflare bootstrap --help resolves on the pinned alchemy@2.0.0-beta.79.
• infra/relay/README.md and docs/operations/release.md describe the new trigger.

What merging this does and does not do

• Merging does not deploy: the workflow file is outside the path filter and the README change is excluded.
• The next deploy (the next relay code change, or a manual run) will be the first successful one since 2026-09-26. It applies everything accumulated since then, including the Alchemy beta.79 migration, so it is worth running by hand and watching rather than letting it ride along with an unrelated merge.
• A change that reaches the relay only through packages/contracts, packages/shared or packages/client-runtime no longer deploys by itself and needs a manual run.

Verification: vp fmt --check on the workflow; CLI help for the new command. The workflow itself has not been run.

This workflow deploys to Cloudflare and Neon, not Vercel. Vercel builds come from the release workflow's hosted web deploy and the marketing deploy; those are not changed here.

Model: Claude Opus 5.5. Harness: Claude Code in Pylon.

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[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	14.0 KiB	+11 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.3 KiB	7.3 KiB	+2 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.7 KiB	6.7 KiB	+9 B (+0.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	9	9	0 (0.0%)	21	✅
Claude	Total thread wire	14.0 KiB	14.0 KiB	−27 B (−0.2%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.3 KiB	7.3 KiB	+9 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.7 KiB	−36 B (−0.5%)	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: 58418d3 · PR result: b88875b · 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: 115.8 KiB
• Claude decoded thread snapshot: 116.5 KiB

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