ci: add comprehensive CI workflow with build, typecheck, lint, and test jobs

Introduce a new GitHub Actions workflow at .github/workflows/ci.yml that runs on push and pull requests to main. It includes four jobs:

- build: checks out code, runs setup action, and builds the project
- typecheck: runs type checking
- lint: runs linting
- test: runs tests

Each job uses the reusable setup action for environment preparation and runs on ubuntu-latest with a 10-minute timeout. This standardizes CI and ensures code quality checks on every push and PR.

Author: koki-develop

.github/workflows/ci.yml

@@ -0,0 +1,70 @@
+name: CI
+
+defaults:
+  run:
+    shell: bash
+
+permissions: {}
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: Build
+    timeout-minutes: 10
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: ./.github/actions/setup
+      - run: bun run build
+
+  typecheck:
+    name: Typecheck
+    timeout-minutes: 10
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: ./.github/actions/setup
+      - run: bun run typecheck
+
+  lint:
+    name: Lint
+    timeout-minutes: 10
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: ./.github/actions/setup
+      - run: bun run lint
+
+  test:
+    name: Test
+    timeout-minutes: 10
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: ./.github/actions/setup
+      - run: bun run test