ci: delete pre-releases matching existing or escaped tags

[zimeg]

Summary

This PR deletes prereleases created from forked pull requests after the branch is deleted.

Preview

Two separate but related issues of lingering prereleases are fixed here:

Dashes to slashes

• https://github.com/slackapi/slack-cli/releases/tag/v3.0.4-dependabot-github_actions-codecov-codecov-action-5.4.2
• https://github.com/slackapi/slack-cli/actions/runs/14474662441/job/40597239855

Identified pre-release tagname to 🔪: v3.0.4-dependabot/github_actions/codecov/codecov-action-5.4.2

Forked tag prefixes

• https://github.com/slackapi/slack-cli/releases/tag/v3.0.4-pull-38-head
• https://github.com/slackapi/slack-cli/actions/runs/14457379870/job/40543395675

Identified pre-release tagname to 🔪: v3.0.4-v3.0.4-pull/35/head

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.93%. Comparing base (fdab4c7) to head (6770a05).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
+ Coverage   62.91%   62.93%   +0.02%     
==========================================
  Files         210      210              
  Lines       22149    22149              
==========================================
+ Hits        13934    13940       +6     
+ Misses       7129     7125       -4     
+ Partials     1086     1084       -2     

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[mwbrooks]

✅ LGTM! Thanks for continuing to tighten up our external contributor process! ✨

[zimeg]

@mwbrooks Thanks so much too for the review 🙏 ✨

I was exploring a lot of unrelated changes in this PR that branched into #42 and #44. These both attempt to address the E2E tests not running for this PR, but AFACT that is instead related to changes of the .github/workflows files 🤖

For now I'm wanting to merge this change to test the actual deletion of this branch. I'll report back with findings, and if all goes well I'll cleanup a few releases made from previous tests.

[zimeg]

📣 So close. The branch deletion event starts workflows on the fork. This makes sense but also might require a follow up PR.

I'll check one more thing before that. Deleting a release or existing tag might start the workflow on this upstream. I'll check both, but follow up still seems needed in either case 👀

[zimeg]

📝 This workflow starts if a tag is deleted. Not releases:

slack-cli/.github/workflows/delete-pr-build-on-close.yml

Lines 6 to 8 in b939841

	on:
	delete:
	branches:

I think the gh command cleans up tags when deleting releases which is how we avoid failed runs most often. For now this seems alright though 🔍

[zimeg]

📝 We are also escaping the branch name of a pull request as expected here! I'm thinking another event might let us used the status of a closed PR to run this workflow when merging forked PRs:

Did not find v3.0.4-pull-38-head tag, trying version prefixes...

https://github.com/slackapi/slack-cli/actions/runs/14525840455/job/40757068833