@W-23938378 | Preserve target-only manifest fields, seed catalog.json only for new apps, and stop PRs into main

[jbisaSF]

Summary

Fixes auto-promote on release/26.8 so a 26.8 → 26.9 hop cannot clobber 26.9-only metadata, rewrite existing catalog.json, or open a PR into main.

Preserve target-only manifest fields

• merge_manifest_entry no longer replaces the whole entry when versions are equal or newer. It merges field-by-field: incoming values update shared keys (version, zip, sha256), and fields that exist only on the target stay.
• That keeps isFeatured, featured*, badge, and companyName on 26.9 — the fields CI: promote from release/26.8 → release/26.9 #113 wiped.
• Older source versions still do not regress the target pin. Adding Approaching Discounts on 26.8 while Avalara is 1.0.0 there and 1.0.1 on 26.9 leaves Avalara at 1.0.1.

catalog.json

• New helper seed_init_catalog_if_absent: writes INIT only when the target has no catalog.json.
• Version bumps of existing apps do not include catalog.json in the auto-promo PR. The target branch's catalog CI job owns version history.

No hop to main

• next_release_branch prints nothing when there is no newer release/*. Auto-promote will not open release/* → main PRs. The newest release branch is the end of the chain.

Workflow wiring

• ZIP selection and apply live in collect_promotable_zips and apply_promoted_zip_onto_target; update-catalog.yml calls them.
• Only ZIPs in the source push (and pinned in the source manifest) are copied. Unlisted siblings (e.g. Avalara when only a new app ZIP changed) are not copied or re-catalogued.

Test plan

• bash .github/scripts/test-promotion-utils.sh — 68 passed, including:
  • equal-version merge keeps target-only keys
  • newer-version merge keeps target-only keys and position
  • whole-file equal-version merge keeps target-only keys (CI: promote from release/26.8 → release/26.9 #113 shape)
  • older source entry does not regress a newer pin (entry and whole-file)
  • new-app promote does not regress a newer target pin (Avalara 1.0.1 + Approaching Discounts)
  • absent catalog is seeded as INIT; existing catalog is skipped and untouched
  • only the changed new-app ZIP is selected; unpinned/missing ZIPs are not
  • new-app ZIP copied + INIT catalog; Avalara 1.0.1 ZIP/catalog unchanged; Avalara 1.0.0 ZIP not copied
  • highest release terminates (does not hop to main)
• Confirm a push to the newest release/* branch does not open a promo PR into main

[shauryemahajanSF]

Test it out on a fork, but LGTM

[jbisaSF]

Test it out on a fork, but LGTM

Verified in the test registry.