Test suite (vitest, 42 tests) and CI workflow

.github/PULL_REQUEST_TEMPLATE.md

@@ -9,6 +9,7 @@
 ## How it was verified
 
 - [ ] `pnpm compile` passes
+- [ ] `pnpm test` passes (add/adjust tests when touching `utils/`)
 - [ ] `pnpm build` produces a clean bundle
 - [ ] Tested in DevTools (extension reloaded + DevTools reopened)
 - [ ] If output format changed: example TOON export attached below

.github/workflows/ci.yml

@@ -0,0 +1,27 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  checks:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - run: pnpm install --frozen-lockfile
+      - run: pnpm wxt prepare # pnpm 10 blocks postinstall scripts
+      - run: pnpm compile # tsc --noEmit
+      - run: pnpm test # vitest run (42 tests over utils/)
+      - run: pnpm build # the extension must still bundle cleanly

CONTRIBUTING.md

@@ -33,11 +33,12 @@ Two invariants to respect:
 
 ```bash
 pnpm compile   # tsc --noEmit, must pass
+pnpm test      # vitest, covers everything under utils/
 pnpm build     # must produce a clean .output/chrome-mv3
 pnpm landing   # optional: rebuilds the landing demo from the fresh bundle
 ```
 
-There is no test runner wired up yet; if you add logic to `utils/`, a small standalone repro in the PR description is appreciated.
+CI runs the same three checks on every pull request. If you touch `utils/`, add or adjust the matching `*.test.ts` next to it: the compaction markers, redaction rules and sourcemap resolution are exactly the kind of logic that regresses silently.
 
 ## Pull requests
 

package.json

@@ -15,11 +15,14 @@
     "zip": "wxt zip",
     "zip:firefox": "wxt zip -b firefox",
     "compile": "tsc --noEmit",
-    "postinstall": "wxt prepare"
+    "postinstall": "wxt prepare",
+    "test": "vitest run"
   },
   "devDependencies": {
     "@resvg/resvg-js": "^2.6.2",
+    "esbuild": "^0.28.1",
     "typescript": "^5.9.3",
+    "vitest": "^4.1.8",
     "wxt": "^0.20.26"
   },
   "dependencies": {