Speed up PR CI critical path (#5147)

## Thinking Path

> - Paperclip orchestrates AI agents for autonomous companies, so
developer throughput on the control plane repo directly affects how fast
the product can evolve.
> - The PR workflow is part of that throughput surface because every
change waits on it before review and merge.
> - This branch started from measured evidence that the PR critical path
was dominated by work that was either serialized unnecessarily or placed
on the wrong part of the graph.
> - The biggest concrete problems were: the canary dry run living inside
`verify`, the server isolated suites running one-by-one in a single
lane, and duplicate CI work that the PR path was paying for without
increasing coverage proportionally.
> - This pull request restructures the PR workflow so those costs are
reduced without removing the important coverage that was already
protecting release and test quality.
> - Follow-up fixes on the branch hardened the new entrypoints so they
work on clean GitHub runners and so the reduced PR typecheck path stays
self-maintaining as workspace packages evolve.
> - The benefit is materially faster PR wall-clock time while keeping
canary packaging checks, serialized-suite isolation, plugin SDK
consumers, and explicit TypeScript coverage where builds do not already
provide it.

## What Changed

- Moved the PR canary dry run into its own `Canary Dry Run` job so it
still runs on PRs but no longer extends the `verify` critical path.
- Split the custom Vitest runner into `general`, `serialized`, and `all`
modes, and added shard support for the isolated server suites.
- Added `test:run:general` and `test:run:serialized` scripts, then
rewired PR CI to fan the serialized server suites out across a 4-way
matrix.
- Added the required `@paperclipai/plugin-sdk` build preflight before
the new reduced-scope typecheck and test entrypoints so they succeed on
clean CI runners.
- Replaced the hardcoded PR build-gap list with
`scripts/run-typecheck-build-gaps.mjs`, which discovers workspace
packages whose `build` scripts skip TypeScript and runs only their
explicit `typecheck` scripts.
- Removed the redundant `pnpm build` from the PR `e2e` job because the
Playwright onboarding path boots Paperclip from source.

## Verification

- `ruby -e "require 'yaml'; YAML.load_file('.github/workflows/pr.yml');
puts 'workflow ok'"`
- `node scripts/run-vitest-stable.mjs --mode general --dry-run`
- `node scripts/run-vitest-stable.mjs --mode serialized --shard-index 0
--shard-count 4 --dry-run`
- `pnpm run typecheck:build-gaps`
- `pnpm test:run:general`
- `pnpm test:run:serialized -- --shard-index 0 --shard-count 4`
- `pnpm build`
- `pnpm paperclipai onboard --yes --run`
- `curl http://127.0.0.1:3299/api/health`

## Risks

- Branch protection or required-check configuration may need to be
updated for the new standalone `Canary Dry Run` job and the
serialized-suite matrix job names.
- `scripts/run-typecheck-build-gaps.mjs` assumes packages that need
explicit PR-time typechecking are the ones whose `build` scripts omit
`tsc`; if build conventions change, that heuristic needs to stay
aligned.
- Serialized test sharding preserves per-suite isolation, but the first
few CI runs should still be watched for shard-balance or naming
assumptions in downstream tooling.

## Model Used

- OpenAI GPT-5.4 via the Codex local adapter, using high reasoning
effort with shell, git, and file-edit tool use in a local worktree.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

.github/workflows/pr.yml

@@ -85,11 +85,11 @@ jobs:
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
 
-      - name: Typecheck
-        run: pnpm -r typecheck
+      - name: Typecheck workspaces whose build scripts skip TypeScript
+        run: pnpm run typecheck:build-gaps
 
-      - name: Run tests
-        run: pnpm test:run
+      - name: Run general test suites
+        run: pnpm test:run:general
 
       - name: Verify release registry test coverage
         run: pnpm run test:release-registry
@@ -97,7 +97,76 @@ jobs:
       - name: Build
         run: pnpm build
 
-      - name: Release canary dry run
+  verify_serialized_server:
+    name: Verify serialized server suites (${{ matrix.shard_label }})
+    needs: [policy]
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - shard_index: 0
+            shard_count: 4
+            shard_label: 1/4
+          - shard_index: 1
+            shard_count: 4
+            shard_label: 2/4
+          - shard_index: 2
+            shard_count: 4
+            shard_label: 3/4
+          - shard_index: 3
+            shard_count: 4
+            shard_label: 4/4
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 9.15.4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Run serialized server test shard
+        run: pnpm test:run:serialized -- --shard-index ${{ matrix.shard_index }} --shard-count ${{ matrix.shard_count }}
+
+  canary_dry_run:
+    name: Canary Dry Run
+    needs: [policy]
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 9.15.4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      # `release.sh` always executes its Step 2/7 workspace build, even when
+      # `--skip-verify` bypasses the initial verification gate.
+      - name: Release canary dry run via release.sh internal build
         run: |
           git checkout -B master HEAD
           git checkout -- pnpm-lock.yaml
@@ -126,9 +195,6 @@ jobs:
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
 
-      - name: Build
-        run: pnpm build
-
       - name: Install Playwright
         run: npx playwright install --with-deps chromium