Add GitHub Actions CI workflow for lint and tests (#79)

.claude/skills/execplans/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: execplans
-description: Write and maintain an ExecPlan — a self-contained, committed Markdown design document in docs/execplans/ — for work that spans more than one session or touches several files or subsystems. Use for a refactor crossing the container/view split, a tooling or dependency migration, replacing the blocked Nightwatch e2e suite, unpicking the two ESLint configs, restoring CI, or any change whose decisions and progress must survive a context reset. Also use when resuming or revising a plan already in docs/execplans/. Invoke with /execplans.
+description: Write and maintain an ExecPlan — a self-contained, committed Markdown design document in docs/execplans/ — for work that spans more than one session or touches several files or subsystems. Use for a refactor crossing the container/view split, a tooling or dependency migration, adding CI or test coverage, #409's chart redraw path, or any change whose decisions and progress must survive a context reset. Also use when resuming or revising a plan already in docs/execplans/. Invoke with /execplans.
 ---
 
 # ExecPlans
@@ -9,8 +9,8 @@ An ExecPlan is a Markdown design document that lives on disk and carries a piece
 design through implementation. It is the durable record: someone holding only the working tree and
 the plan file can pick the work up and finish it. Write one instead of relying on the built-in
 plan/todo tools whenever the work meets the threshold below — those tools don't survive a context
-reset, and this repo's near-term work (restoring CI, unifying the two ESLint configs, replacing the
-blocked Nightwatch suite) is exactly the kind that needs to.
+reset, and this repo's near-term work (adding CI, broadening test coverage, fixing #409's chart
+redraw path) is exactly the kind that needs to.
 
 Plans in this repository go in `docs/execplans/` and are committed on the working branch. **Read
 `references/PLANS.md` in full before writing or revising one** — it is the specification, and its
@@ -44,6 +44,8 @@ Skip it for a single-file fix, a copy change, or anything a commit title already
    see the addendum's "Committing" section for the exact scope.
 6. Commit the plan on its own, before the first implementation commit. Then implement, updating
    `Progress`, `Surprises & Discoveries`, and `Decision Log` in the same commits as the work.
+   Record consequential decisions and surprises, not routine development operations — see the
+   addendum's "Record what matters, not what happened".
 7. Write `Outcomes & Retrospective` when the work lands, and commit that too.
 
 ## Resuming

.github/workflows/ci.yml

@@ -0,0 +1,59 @@
+name: CI
+
+on:
+    push:
+        branches:
+            - main
+    pull_request:
+
+concurrency:
+    group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+    cancel-in-progress: true
+
+permissions:
+    contents: read
+
+jobs:
+    lint-and-test:
+        name: Lint and test
+        runs-on: ubuntu-latest
+        timeout-minutes: 10
+        if: github.repository == 'mozilla/ensemble'
+        steps:
+            - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+              with:
+                  persist-credentials: false
+            - uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+              with:
+                  node-version-file: '.nvmrc'
+                  cache: npm
+            - name: Install dependencies
+              run: npm ci
+            - name: Compile Stylus
+              run: npm run build:css
+            - name: Run lint
+              run: npm run lint
+            - name: Run unit tests
+              run: npm run test:jest
+
+    e2e:
+        name: End-to-end tests
+        runs-on: ubuntu-latest
+        timeout-minutes: 20
+        if: github.repository == 'mozilla/ensemble'
+        steps:
+            - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+              with:
+                  persist-credentials: false
+            - uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+              with:
+                  node-version-file: '.nvmrc'
+                  cache: npm
+            - name: Install dependencies
+              run: npm ci
+            - name: Install Playwright browsers
+              run: npx playwright install --with-deps chromium
+            - name: Compile Stylus
+              run: npm run build:css
+            - name: Run end-to-end tests
+              run: npm run test:playwright