ops(ci): harden authorisation, migrate notify-slack action to TypeScript, and remove dead workflows

.github/actions/notify-slack-publish-status/.gitignore

@@ -0,0 +1,4 @@
+node_modules
+*.tsbuildinfo
+.eslintcache
+!dist/

.github/actions/notify-slack-publish-status/.prettierignore

@@ -0,0 +1,3 @@
+dist/
+node_modules/
+pnpm-lock.yaml

.github/actions/notify-slack-publish-status/action.yml

@@ -1,11 +1,14 @@
 ---
-name: 'Notify Slack Publish Status'
-description: 'Notify Slack with the completion status of the publish action'
+name: "Notify Slack Publish Status"
+description: "Notify Slack with the completion status of the publish action"
 inputs:
+  webhook:
+    description: "Slack incoming webhook URL"
+    required: true
   message:
-    description: 'Message to send to Slack'
+    description: "Message to send to Slack"
     required: true
-    default: ''
+    default: ""
 runs:
-  using: 'node20'
-  main: 'index.js'
+  using: "node24"
+  main: "dist/index.js"