feat: add prek pre-commit hooks and dependabot (#1720)

* feat: add prek pre-commit hooks and dependabot

Pre-commit hooks (via prek):
- Basic hygiene: trailing-whitespace, end-of-file-fixer, check-yaml, check-added-large-files, check-merge-conflict
- Security: detect-secrets, zizmor (GitHub Actions audit)
- Linting: shellcheck, actionlint, oxlint, swiftlint
- Formatting: oxfmt, swiftformat

Dependabot:
- npm and GitHub Actions ecosystems
- Grouped updates (production/development/actions)
- 7-day cooldown for supply chain protection

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: add prek install instruction to AGENTS.md

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

.github/actionlint.yaml

@@ -0,0 +1,17 @@
+# actionlint configuration
+# https://github.com/rhysd/actionlint/blob/main/docs/config.md
+
+self-hosted-runner:
+  labels:
+    # Blacksmith CI runners
+    - blacksmith-4vcpu-ubuntu-2404
+    - blacksmith-4vcpu-windows-2025
+
+# Ignore patterns for known issues
+paths:
+  .github/workflows/**/*.yml:
+    ignore:
+      # Ignore shellcheck warnings (we run shellcheck separately)
+      - 'shellcheck reported issue.+'
+      # Ignore intentional if: false for disabled jobs
+      - 'constant expression "false" in condition'

.github/dependabot.yml

@@ -0,0 +1,113 @@
+# Dependabot configuration
+# https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+
+registries:
+  npm-npmjs:
+    type: npm-registry
+    url: https://registry.npmjs.org
+    replaces-base: true
+
+updates:
+  # npm dependencies (root)
+  - package-ecosystem: npm
+    directory: /
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    groups:
+      production:
+        dependency-type: production
+        update-types:
+          - minor
+          - patch
+      development:
+        dependency-type: development
+        update-types:
+          - minor
+          - patch
+    open-pull-requests-limit: 10
+    registries:
+      - npm-npmjs
+
+  # GitHub Actions
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    groups:
+      actions:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+    open-pull-requests-limit: 5
+
+  # Swift Package Manager - macOS app
+  - package-ecosystem: swift
+    directory: /apps/macos
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    groups:
+      swift-deps:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+    open-pull-requests-limit: 5
+
+  # Swift Package Manager - shared ClawdbotKit
+  - package-ecosystem: swift
+    directory: /apps/shared/ClawdbotKit
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    groups:
+      swift-deps:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+    open-pull-requests-limit: 5
+
+  # Swift Package Manager - Swabble
+  - package-ecosystem: swift
+    directory: /Swabble
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    groups:
+      swift-deps:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+    open-pull-requests-limit: 5
+
+  # Gradle - Android app
+  - package-ecosystem: gradle
+    directory: /apps/android
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    groups:
+      android-deps:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+    open-pull-requests-limit: 5