ci: automatically categorize pull requests

.github/PR_LABELS.md

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+# Automatic PR labels
+
+The `Label pull requests` workflow categorizes new and updated pull requests,
+including contributions from forks. It becomes active when merged into the
+default branch. Existing PRs are labeled on their next update or title edit.
+
+- `area: ...` labels match changed paths in `.github/labeler.yml`. Multiple
+  areas can apply to one PR.
+- `type: ...` labels match Conventional Commit prefixes in the PR title:
+  `fix`, `feat`, `docs`, `refactor`, `perf`, `test`, `build`, `ci`, `chore`,
+  `style`, and `revert`. An optional scope is supported.
+- For example, `fix(device): restore DPI settings` gets `type: bug`, and
+  `feat(ui)!: replace profile editor` gets `type: enhancement` and
+  `type: breaking`. Titles without a recognized prefix get no type label;
+  this workflow does not enforce a title format.
+
+Automation creates missing labels and removes its own labels when they no
+longer match. Reserve the configured `area:` and `type:` labels for automation;
+other labels, including the standard `bug` and `enhancement` labels, are left
+for manual triage. Existing label colors and descriptions are preserved.
+
+The workflow uses `pull_request_target` with API access only. Do not add a PR
+checkout or execute contributor-provided code in this workflow. `issues: write`
+allows creation of repository labels, and `pull-requests: write` allows labeling
+PRs. Both actions are pinned to commit SHAs.

.github/labeler.yml

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+"area: native":
+  - changed-files:
+      - any-glob-to-any-file: ["src/**"]
+"area: devices":
+  - changed-files:
+      - any-glob-to-any-file: ["src/hid.rs", "src/drivers/**", "native-hid/**"]
+"area: overlay":
+  - changed-files:
+      - any-glob-to-any-file: ["src/overlay/**"]
+"area: packaging":
+  - changed-files:
+      - any-glob-to-any-file: ["install-*.sh", "assets/**"]
+"area: documentation":
+  - changed-files:
+      - any-glob-to-any-file: ["**/*.md", "**/*.mdx", "docs/**"]
+"area: dependencies":
+  - changed-files:
+      - any-glob-to-any-file: ["**/package.json", "**/package-lock.json", "**/Cargo.toml", "**/Cargo.lock"]
+"area: ci":
+  - changed-files:
+      - any-glob-to-any-file: [".github/**", "build/**", "scripts/**", "**/build.rs", "vite.config.*", "tsconfig*.json"]

.github/workflows/label-pr.yml

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+name: Label pull requests
+
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronize, edited, ready_for_review]
+
+permissions:
+  contents: read
+  pull-requests: write
+  issues: write
+
+concurrency:
+  group: label-pr-${{ github.event.pull_request.number }}
+  cancel-in-progress: false
+
+jobs:
+  label:
+    runs-on: ubuntu-latest
+    steps:
+      # Read metadata through the API; never check out or execute PR code.
+      - name: Ensure labels exist and categorize the current title
+        uses: actions/github-script@373c709c69115d41ff229c7e5df9f8788daa9553 # v9
+        with:
+          script: |
+            const repo = context.repo;
+            const issue_number = context.payload.pull_request.number;
+            const areas = {
+              "native": "Native bridge and platform services",
+              "devices": "HID access and device drivers",
+              "overlay": "Desktop overlay",
+              "packaging": "Installation and application assets",
+              "documentation": "Documentation",
+              "dependencies": "Dependency manifests and lockfiles",
+              "ci": "Automation and build configuration",
+            };
+            const types = {
+              fix: 'bug', feat: 'enhancement', docs: 'documentation',
+              refactor: 'refactor', perf: 'performance', test: 'tests',
+              build: 'build', ci: 'ci', chore: 'maintenance',
+              style: 'style', revert: 'revert',
+            };
+            const definitions = [
+              ...Object.entries(areas).map(([area, description]) => ({
+                name: `area: ${area}`, color: '1d76db', description,
+              })),
+              ...Object.values(types).map(type => ({
+                name: `type: ${type}`, color: '5319e7',
+                description: `PR title category: ${type}`,
+              })),
+              { name: 'type: breaking', color: 'd93f0b', description: 'PR title declares a breaking change with !' },
+            ];
+            const existing = new Set((await github.paginate(
+              github.rest.issues.listLabelsForRepo, { ...repo, per_page: 100 }
+            )).map(label => label.name));
+            for (const definition of definitions) {
+              if (existing.has(definition.name)) continue;
+              try {
+                await github.rest.issues.createLabel({ ...repo, ...definition });
+              } catch (error) {
+                // Another PR's workflow may have created the same label.
+                if (error.status !== 422 || !error.response?.data?.errors?.some(
+                  item => item.code === 'already_exists'
+                )) throw error;
+              }
+            }
+            // Fetch the latest title so queued events do not restore stale categories.
+            const { data: pr } = await github.rest.pulls.get({
+              ...repo, pull_number: issue_number,
+            });
+            const match = pr.title.trim().match(
+              /^(fix|feat|docs|refactor|perf|test|build|ci|chore|style|revert)(?:\([^)\r\n]+\))?(!)?:\s+\S/i
+            );
+            const desired = new Set();
+            if (match) {
+              desired.add(`type: ${types[match[1].toLowerCase()]}`);
+              if (match[2]) desired.add('type: breaking');
+            }
+            const managed = new Set([
+              ...Object.values(types).map(type => `type: ${type}`), 'type: breaking',
+            ]);
+            for (const label of pr.labels) {
+              if (managed.has(label.name) && !desired.has(label.name)) {
+                await github.rest.issues.removeLabel({ ...repo, issue_number, name: label.name });
+              }
+            }
+            if (desired.size) {
+              await github.rest.issues.addLabels({ ...repo, issue_number, labels: [...desired] });
+            }
+
+      - name: Categorize changed files
+        uses: actions/labeler@bf12e9b00b37c5c0ca2b87b79b2daf7891dbda13 # v7
+        with:
+          sync-labels: true