fix(rt-v1): restore jellyfish-deploy-notification as no-op stub

[pdodgen-revparts]

Symptom

encodium/internal_api run 29114404344 — hotfix-SHOP-5216 workflow_dispatch → startup_failure.

Root cause: hotfix-SHOP-5216 was cut from main BEFORE today's sweep merged. Its deploy-eks.yaml (line 27) still has uses: encodium/.github/.github/workflows/jellyfish-deploy-notification.yaml@main. GH runs startup validation over the entire reusable-workflow tree even for jobs that would be if:-gated off. Since I deleted the shared workflow in #152 (a3b0afc), tree resolution fails before any job runs.

Every long-lived branch across the org that predates the sweep (feature branches, hotfix-*, dependabot PRs, in-flight work) has the same footgun.

Fix (this PR)

Restore jellyfish-deploy-notification.yaml as a no-op stub:

• Same workflow_call input + secret signature as the deleted original → callers resolve cleanly
• Job body does nothing except log a deprecation ::notice:: pointing at the retirement history
• No API call to Jellyfish. No side effects. Never fails.

Long-lived branches stop hitting startup_failure immediately.

Not this PR — the retirement itself stands

• All 22 participant sweep PRs stay merged
• Per-repo jellyfish-notify job removals stay in place
• Deletion of Jellyfish call itself in chore: delete jellyfish-deploy-notification.yaml — no more callers (DEVEX-1653) #152 is effectively preserved (the stub doesn't call Jellyfish)

Delete-for-real timeline

Once org-wide branch churn has cycled through (rough guideline: ~1 month), delete this stub in a follow-up. Anything actively worked on will have naturally rebased/merged and dropped the stale reference.

[cursor]

PR Summary

Low Risk
CI-only change with no runtime, auth, or data impact; the stub intentionally does nothing beyond logging a notice.

Overview
Restores the shared reusable workflow jellyfish-deploy-notification.yaml that was removed in #152, but only as a no-op stub so older branches still resolve the workflow at startup.

The stub keeps the same workflow_call inputs (environment, image_tag) and jellyfish_api_token secret so existing uses: references on long-lived branches no longer cause workflow_dispatch startup_failure when GitHub validates the reusable-workflow tree. The single job only emits a deprecation ::notice—no Jellyfish API calls or other side effects.

Per-repo Jellyfish job removals from the org sweep are unchanged; this is a compatibility bridge until branch churn drops stale references (~1 month), after which the stub can be deleted again.

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