ci(lotus): remove the cached corepack pnpm shim before installing pnpm

Run #1855: `npm install -g pnpm@…` failed with EEXIST because the runner's
persistent hostedtoolcache Node install still carries the corepack `pnpm`
shim from earlier `corepack enable` runs, and npm won't overwrite it.
Disable/remove the shim first, then install, and print the version so the
log shows which pnpm actually ran.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

.gitea/workflows/ci.yml

@@ -56,7 +56,15 @@ jobs:
       # pinned version itself. Version is read from package.json's
       # packageManager field so it cannot drift from the lockfile.
       - name: Install pnpm (version from packageManager field)
-        run: npm install -g "pnpm@$(node -p "require('./package.json').packageManager.split('@')[1].split('+')[0]")"
+        # The runner's cached Node toolchain keeps a corepack `pnpm` shim from
+        # earlier runs, and npm refuses to overwrite it (EEXIST, run #1855) —
+        # drop the shim first so the real binary lands.
+        run: |
+          B="$(dirname "$(command -v node)")"
+          corepack disable pnpm 2>/dev/null || true
+          rm -f "$B/pnpm" "$B/pnpx"
+          npm install -g "pnpm@$(node -p "require('./package.json').packageManager.split('@')[1].split('+')[0]")"
+          pnpm --version
 
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
@@ -125,7 +133,15 @@ jobs:
       # pinned version itself. Version is read from package.json's
       # packageManager field so it cannot drift from the lockfile.
       - name: Install pnpm (version from packageManager field)
-        run: npm install -g "pnpm@$(node -p "require('./package.json').packageManager.split('@')[1].split('+')[0]")"
+        # The runner's cached Node toolchain keeps a corepack `pnpm` shim from
+        # earlier runs, and npm refuses to overwrite it (EEXIST, run #1855) —
+        # drop the shim first so the real binary lands.
+        run: |
+          B="$(dirname "$(command -v node)")"
+          corepack disable pnpm 2>/dev/null || true
+          rm -f "$B/pnpm" "$B/pnpx"
+          npm install -g "pnpm@$(node -p "require('./package.json').packageManager.split('@')[1].split('+')[0]")"
+          pnpm --version
 
       - name: Install dependencies
         run: pnpm install --frozen-lockfile