[ty] Automatically re-run ecosystem-analyzer workflow on subsequent pushes to a PR, if the PR has the ecosystem-analyzer label (#22179)

## Summary

This PR reworks our ecosystem-analyzer workflow so that it automatically
reruns if a PR with the `ecosystem-analyzer` label has new commits
pushed to it, or is reopened after previously being closed. It's
currently easy to forget that you need to remove and re-add the label to
trigger a fresh workflow run, which can then mean that there are stale
(misleading) results in the PR comment posted by the bot. It also means
that it takes longer for CI to finish than it would otherwise, because
it might be a few minutes after pushing new commits to the PR before you
remember that you also need to remove and re-add the label.

To write this PR, I consulted:
- The GitHub workflow trigger documentation:
https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows#pull_request
- This Stack Overflow answer:
https://stackoverflow.com/a/59588725/13990016

## Test Plan

I experimented with pushing commits to this PR and closing/reopening it,
and both of these actions triggered fresh runs of the ecosystem-analyzer
worfklow when the label was present on the PR. However, removing the
label again meant that the workflow was no longer triggered by these
actions.

.github/workflows/ty-ecosystem-analyzer.yaml

@@ -4,7 +4,13 @@ permissions: {}
 
 on:
   pull_request:
-    types: [labeled]
+    # The default for `pull_request` is to trigger on `synchronize`, `opened` and `reopened`.
+    # We also add `labeled` here so that the workflow triggers when a label is initially added.
+    types:
+      - labeled
+      - synchronize
+      - opened
+      - reopened
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref_name }}-${{ github.event.pull_request.number || github.sha }}
@@ -23,7 +29,7 @@ jobs:
     name: Compute diagnostic diff
     runs-on: ${{ github.repository == 'astral-sh/ruff' && 'depot-ubuntu-22.04-32' || 'ubuntu-latest' }}
     timeout-minutes: 20
-    if: contains(github.event.label.name, 'ecosystem-analyzer')
+    if: contains( github.event.pull_request.labels.*.name, 'ecosystem-analyzer')
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:

.github/workflows/ty-ecosystem-report.yaml

@@ -1,3 +1,7 @@
+# This workflow is a cron job that generates a report describing
+# all diagnostics ty emits across the whole ecosystem. The report
+# is uploaded to https://ty-ecosystem-ext.pages.dev/ on a weekly basis.
+
 name: ty ecosystem-report
 
 permissions: {}