Revert projects-per-job to 4 and restore target/ cleanup

Keeping target/ between Anchor projects backfired — each project has its
own Cargo workspace so the build cache from one doesn't help the next,
and the accumulated artifacts slow down subsequent builds. Anchor wall
clock went from 18 min to 34 min.

Reverting MIN_PROJECTS_PER_JOB back to 4 (more parallel jobs with less
work each = faster wall clock) and restoring rm -rf target cleanup.

The cargo registry cache (actions/cache) is still in place — that caches
downloaded crate tarballs which ARE shared across projects.

Author: mikemaccana-edwardbot

.github/workflows/anchor.yml

@@ -15,7 +15,7 @@ concurrency:
 
 env:
   MAX_JOBS: 64
-  MIN_PROJECTS_PER_JOB: 8
+  MIN_PROJECTS_PER_JOB: 4
   MIN_PROJECTS_FOR_MATRIX: 4
   # See https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/
   FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
@@ -175,6 +175,7 @@ jobs:
             if ! anchor build; then
               echo "::error::anchor build failed for $project"
               echo "$project: anchor build failed" >> $GITHUB_WORKSPACE/failed_projects.txt
+              rm -rf target node_modules
               cd - > /dev/null
               return 1
             fi
@@ -183,13 +184,13 @@ jobs:
             if ! anchor test; then
               echo "::error::anchor test failed for $project"
               echo "$project: anchor test failed" >> $GITHUB_WORKSPACE/failed_projects.txt
-              rm -rf node_modules
+              rm -rf target node_modules
               cd - > /dev/null
               return 1
             fi
 
             echo "Build and tests succeeded for $project."
-            rm -rf node_modules
+            rm -rf target node_modules
             cd - > /dev/null
             return 0
           }

.github/workflows/native.yml

@@ -15,7 +15,7 @@ concurrency:
 
 env:
   MAX_JOBS: 64
-  MIN_PROJECTS_PER_JOB: 8
+  MIN_PROJECTS_PER_JOB: 4
   MIN_PROJECTS_FOR_MATRIX: 4
   # See https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/
   FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true

.github/workflows/pinocchio.yml

@@ -15,7 +15,7 @@ concurrency:
 
 env:
   MAX_JOBS: 64
-  MIN_PROJECTS_PER_JOB: 8
+  MIN_PROJECTS_PER_JOB: 4
   MIN_PROJECTS_FOR_MATRIX: 4
   # See https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/
   FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true

.github/workflows/quasar.yml

@@ -15,7 +15,7 @@ concurrency:
 
 env:
   MAX_JOBS: 64
-  MIN_PROJECTS_PER_JOB: 8
+  MIN_PROJECTS_PER_JOB: 4
   MIN_PROJECTS_FOR_MATRIX: 4
   # Force all JavaScript-based actions to use Node.js 24 runtime.
   # Node.js 20 actions are deprecated and will stop working June 2026.