feat: add sync-main-to-edge workflow + .gitupstream

[alex-nsheaps]

Summary

Adds the edge-sync consumer workflow + .gitupstream config to this repo. The workflow delegates to the reusable workflow in nsheaps/github-actions#24; the config lists which */edge branches to keep in sync with main.

• .github/workflows/sync-main-to-edge.yaml — fires on push-to-main (and workflow_dispatch)
• .gitupstream — YAML config listing edge targets

The workflow file is also distributed by nsheaps/.github#63 via sync-files; we're seeding it here so the repo works standalone and sync-files will pick up from there idempotently.

Depends on

• nsheaps/github-actions#24 — reusable workflow MUST land first.

Test plan

• Merge after github-actions#24 lands
• Verify next push to main triggers the workflow and syncs configured edge branches (no-op when targets already up-to-date or missing)

Open Questions

1. For repos without an existing edge branch, .gitupstream currently has sync: [] as a placeholder. Should I instead pre-seed with alex/edge even though the branch doesn't exist? The reusable workflow skips missing targets, so either works.
2. The workflow uses: points at @main (the reusable). Want a SHA-pin instead for reproducibility?

Refs nsheaps/.ai-agent-alex#685.

🤖 Generated with Claude Code

Decisions (Q1/Q2/Q3 follow-up 2026-05-28)

Nate answered the original Open Questions (Discord msg):

• Q1 (ref pinning): Keep uses: ...@main for the reusable.
• Q2 (placeholder .gitupstream): Seed each agent repo with <agent>/edge target + create the branch. Done in this PR set; alex/edge, jack/edge, henry/edge now exist on their respective repos.
• Q3 (triggers): All three — push: branches:[main], schedule: '0 6 * * *' (nightly UTC), workflow_dispatch:.

Full follow-up: https://github.com/nsheaps/.ai-agent-alex/blob/main/docs/journal/2026/05/28/edge-sync-q2q3-followup.md

[henry-nsheaps]

👍 Already merged — recap + one open follow-up

✅ PR merged at 20:55:10Z; dep nsheaps/github-actions#24 merged 75s earlier at 20:53:55Z — merge ordering OK
✅ Reusable workflow now on main of nsheaps/github-actions (verified via contents API)
✅ test_mode boolean coercion safe across triggers (verified previously)
✅ .gitupstream schema matches reusable workflow's yq parser
⚠️ Still on @main ref — repo convention is SHA-pin; tracking as a follow-up

🖱️ Click to expand for full details

State at review time

This PR is already merged (by @nsheaps at 2026-05-28T20:55:10Z). This is a post-merge follow-up review consolidating what was flagged previously.

What resolved itself

• Merge ordering (thread): nsheaps/github-actions#24 landed first (20:53:55Z vs 20:55:10Z), so the first push-to-main after merge had the reusable workflow available. Thread resolved.
• Open question #1 (pre-seed alex/edge): confirmed safe — reusable workflow skips missing targets.
• test_mode coercion: verified across push, workflow_dispatch default, and workflow_dispatch true paths.

What's still open (non-blocking, follow-up only)

• SHA-pin (thread): uses: nsheaps/github-actions/.github/workflows/sync-main-to-edge.yaml@main was merged as-is. Every other nsheaps/github-actions reference in this repo is SHA-pinned per .claude/rules/ci-cd/conventions.md. Because this file is sync-files–managed from nsheaps/.github, the pin needs to land in the upstream template (nsheaps/.github#63) — otherwise any direct edit here would revert on the next sync.

Scoring rationale

• Quality 95%: same as prior review — clean, minimal, well-commented. -5 for the unresolved @main deviation from repo convention (still present in merged code).
• Security 85%: unchanged — @main for a contents: write reusable workflow is the only risk; same-org so blast radius is low.
• Simplicity 100%: two small files, no abstractions beyond what's needed.
• Confidence 98%: +3 over prior review now that both the dep workflow file and this PR are on main and verifiable.

Recommended follow-ups (non-blocking):

• SHA-pin the reusable workflow ref. Best done by updating the template in nsheaps/.github#63 so the next sync-files run propagates a pinned @<sha> # sync-main-to-edge@main form into all consumer repos. Direct edits here will be overwritten.
• Optional: explicitly set config_path: .gitupstream in the caller for future-proofing if the schema location ever moves (currently defaulting is fine).

Notes:¹²³⁴⁵

Footnotes

1. Workflow Run: https://github.com/nsheaps/ai-mktpl/actions/runs/26601481970/attempts/1 ↩

2. PR: #559 ↩

3. Dependency PR (now merged): nsheaps/github-actions#24 ↩

4. Distribution PR (sync-files template): nsheaps/.github#63 ↩

5. Repo CI/CD conventions: .claude/rules/ci-cd/conventions.md ↩