feat: Add digital, dry, ink, and paint brush presets; implement regression testing hooks

- Introduced new crates for digital brushes, dry media brushes, ink brushes, and paint brushes, each containing various presets.
- Updated the menus to include "Paste Special" and "Paste as New Layer" options.
- Enhanced the feature scorecard tests to validate selection texture encoding.
- Added a regression gate workflow for automated testing on push and pull requests.
- Implemented Git hooks for pre-commit checks to ensure code formatting and run tests before commits.
- Created a settings file for local configurations.

.gitea/workflows/regression-gate.yml

@@ -0,0 +1,26 @@
+name: mandatory-regression-gate
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  deterministic-tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Reject commit whitespace errors
+        run: git show --check --oneline --no-patch HEAD
+      - name: Run deterministic workspace tests
+        run: |
+          cargo check --locked --workspace --exclude hcie-io --examples
+          cargo test --locked --workspace --exclude hcie-io --lib --tests -- --skip benchmark_4k_stroke_on_multilayer_document
+      - name: Run protected visual regression tests
+        run: cargo test --locked -p hcie-engine-api --test visual_regression
+
+  protected-performance-path:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Verify protected 4K stroke path
+        run: cargo test --locked -p hcie-engine-api --test performance_stroke_4k -- --nocapture