Point the ecosystem URL check at pnpm and the right paths

The job has been failing on every push since the redesign, for two reasons both
introduced by it. It runs `npm ci` behind `cache: npm`, which needs the
package-lock.json deleted when the lockfiles were reconciled — the repo pins
pnpm via packageManager and ships pnpm-lock.yaml. And it triggers on
data/ecosystem.json, which is the catalogue's old shape; the data moved to
markdown in content/ecosystem, so the guard had quietly stopped firing on the
files it exists to check.

The script itself was fine: it already reads content/ecosystem, and passes
locally at 12 URLs checked, 0 failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: adamsoffer

.github/workflows/check-ecosystem-urls.yml

@@ -1,10 +1,12 @@
 name: Check Ecosystem URLs
 
 on:
-  # Run on PRs that touch ecosystem data
+  # Run on PRs that touch ecosystem data. The catalogue is markdown in
+  # content/ecosystem — data/ecosystem.json was its old shape and no longer
+  # exists, so this trigger had stopped firing on the files it is meant to guard.
   pull_request:
     paths:
-      - "data/ecosystem.json"
+      - "content/ecosystem/**"
       - "public/ecosystem/**"
 
   # Weekly check — Mondays at 9am UTC
@@ -20,13 +22,18 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      # pnpm, not npm: the repo pins it via package.json's packageManager field
+      # and ships pnpm-lock.yaml. This step must precede setup-node so that
+      # `cache: pnpm` can find the store.
+      - uses: pnpm/action-setup@v4
+
       - uses: actions/setup-node@v4
         with:
           node-version: 20
-          cache: npm
+          cache: pnpm
 
       - name: Install dependencies
-        run: npm ci
+        run: pnpm install --frozen-lockfile
 
       - name: Check ecosystem URLs
         run: node scripts/check-ecosystem-urls.mjs