Spike: Define Slack trigger pattern for Publish Starter workflow launcher

[dcolina]

Description

Before implementing a Slack-based launcher for the Publish Starter workflow, we need to investigate and align on the correct pattern. Goal: identify the existing Slack trigger pattern used in other team applications (Bolt app, Workflow Builder, Lambda, etc.), evaluate fit for triggering workflow_dispatch on cicd_manual_publish-starter.yml, and produce an implementation decision with chosen approach, required infra, and secrets/vars needed. Output of this spike: an updated implementation plan for the launcher feature and a well-defined follow-up Task issue.

Acceptance Criteria

• [Define what needs to be accomplished]

Additional Notes

[Any additional context or notes]