ci: eliminate cold pnpm install via pre-baked CI base image (Phase 1) (#635)

.woodpecker/publish.yml

@@ -2,7 +2,9 @@
 # Runs only on main branch push/tag
 
 variables:
-  - &node_image 'node:22-alpine'
+  # Pre-baked CI base (see .woodpecker/ci-image.yml): node:22-alpine +
+  # toolchain + warm pnpm store. Kills the second cold install publish pays.
+  - &node_image 'git.mosaicstack.dev/mosaicstack/stack/ci-base:latest'
   - &enable_pnpm 'corepack enable'
   # Heavy kaniko image builds (~25 min) — gate them so a merge that only touches
   # the npm-only CLI (@mosaicstack/mosaic) or docs does NOT rebuild the platform
@@ -31,7 +33,8 @@ steps:
     image: *node_image
     commands:
       - corepack enable
-      - pnpm install --frozen-lockfile
+      # Resolve from the baked pnpm store instead of a cold network fetch.
+      - pnpm install --frozen-lockfile --prefer-offline
 
   build:
     image: *node_image