Remove per-repo GHA slash command workflows after dogfooding migration

[vdemeester]

Parent

Part of #3121 — Migrate slash commands from GitHub Actions to dogfooding cluster

Summary

After the slash commands are successfully running on the dogfooding cluster, remove the per-repo GitHub Actions workflow files from all consumer repositories.

Files to Remove Per Repo

Each consumer repo has some combination of:

• .github/workflows/slash.yml or .github/workflows/slash.yaml — routing
• .github/workflows/cherry-pick-command.yaml — cherry-pick handler
• .github/workflows/rebase-command.yaml — rebase handler
• .github/workflows/chatops_retest.yaml / chatops-retest.yml — retest handler

Current Inventory

Repo	slash	cherry-pick-command	rebase-command	chatops_retest
pipeline	✅	✅	✅	✅
chains	✅	✅	❌	✅
dashboard	✅	✅	❌	✅
cli	✅	❌	❌	✅
operator	✅	✅	❌	✅
mcp-server	✅	✅	❌	✅
pruner	✅	✅	❌	✅

Plumbing repo (reusable workflow definitions)

• .github/workflows/_slash.yml
• .github/workflows/_cherry-pick-command.yaml
• .github/workflows/_rebase-command.yaml
• .github/workflows/_chatops_retest.yml

Approach

1. Run both GHA and Tekton versions in parallel for a testing period
2. Verify Tekton versions work correctly across all repos
3. Remove per-repo GHA files via PRs to each repo
4. Remove reusable workflow definitions from plumbing
5. Update documentation

Acceptance Criteria

• All per-repo GHA slash command workflow files removed
• Reusable workflow definitions removed from plumbing
• Slash commands continue to work via dogfooding cluster
• Documentation updated