ci(lint): stop re-running heavy jobs on PR title edits

The quality gate ran its full matrix on every PR edit event even though
title/body edits cannot change the code: only validate_pr_title needs
them. Gate the heavy jobs on action != 'edited', add the missing
concurrency group (Renovate PRs currently run the whole gate twice per
commit), cache Bun dependencies like the other workflows, drop the
unused setup-node step, and run checkout/Bun setup in parallel.

.github/workflows/linting.yml

@@ -11,6 +11,10 @@ on:
 permissions:
   contents: read
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   validate_pr_title:
     name: "📝 Validate PR Title"
@@ -46,6 +50,8 @@ jobs:
 
   dependency-review:
     name: 🔍 Vulnerable Dependencies
+    # PR title/body edits can't change the dependency graph — only re-run on code events.
+    if: github.event.action != 'edited'
     runs-on: ubuntu-26.04
     permissions:
       contents: read
@@ -65,20 +71,31 @@ jobs:
 
   expo-doctor:
     name: 🚑 Expo Doctor Check
+    # PR title/body edits can't change the project — only re-run on code events.
+    if: github.event.action != 'edited'
     runs-on: ubuntu-26.04
     steps:
-      - name: 🛒 Checkout repository
-        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
-        with:
-          ref: ${{ github.event.pull_request.head.sha || github.sha }}
-          submodules: recursive
-          fetch-depth: 0
+      - parallel:
+          - name: 🛒 Checkout repository
+            uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+            with:
+              ref: ${{ github.event.pull_request.head.sha || github.sha }}
+              submodules: recursive
+              fetch-depth: 0
 
-      - name: 🍞 Setup Bun
-        uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # v2.2.0
+          - name: 🍞 Setup Bun
+            uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # v2.2.0
+            with:
+              # renovate: datasource=npm depName=bun
+              bun-version: "1.3.14"
+
+      - name: 💾 Cache Bun dependencies
+        uses: actions/cache@2c8a9bd7457de244a408f35966fab2fb45fda9c8 # v6.0.0
         with:
-          # renovate: datasource=npm depName=bun
-          bun-version: "1.3.14"
+          path: ~/.bun/install/cache
+          key: ${{ runner.os }}-${{ runner.arch }}-bun-${{ hashFiles('bun.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-${{ runner.arch }}-bun-
 
       - name: 📦 Install dependencies (bun)
         run: bun install --frozen-lockfile
@@ -91,6 +108,8 @@ jobs:
 
   code_quality:
     name: "🔍 Lint & Test (${{ matrix.command }})"
+    # PR title/body edits can't change the code — only re-run on code events.
+    if: github.event.action != 'edited'
     runs-on: ubuntu-26.04
     strategy:
       fail-fast: false
@@ -103,24 +122,27 @@ jobs:
           - "i18n:check"
 
     steps:
-      - name: "📥 Checkout PR code"
-        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
-        with:
-          ref: ${{ github.event.pull_request.head.sha || github.sha }}
-          submodules: recursive
-          fetch-depth: 0
+      - parallel:
+          - name: "📥 Checkout PR code"
+            uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+            with:
+              ref: ${{ github.event.pull_request.head.sha || github.sha }}
+              submodules: recursive
+              fetch-depth: 0
 
-      - name: "🟢 Setup Node.js"
-        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
-        with:
-          # renovate: datasource=node-version depName=node versioning=node
-          node-version: "24.18.0"
+          - name: "🍞 Setup Bun"
+            uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # v2.2.0
+            with:
+              # renovate: datasource=npm depName=bun
+              bun-version: "1.3.14"
 
-      - name: "🍞 Setup Bun"
-        uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # v2.2.0
+      - name: 💾 Cache Bun dependencies
+        uses: actions/cache@2c8a9bd7457de244a408f35966fab2fb45fda9c8 # v6.0.0
         with:
-          # renovate: datasource=npm depName=bun
-          bun-version: "1.3.14"
+          path: ~/.bun/install/cache
+          key: ${{ runner.os }}-${{ runner.arch }}-bun-${{ hashFiles('bun.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-${{ runner.arch }}-bun-
 
       - name: "📦 Install dependencies"
         run: bun install --frozen-lockfile