Add native Go port of Rough.js 4.0.4

.github/workflows/ci.yml

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+name: ci
+
+on: [push, pull_request]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-go@v6
+        with:
+          go-version-file: go.mod
+          cache: true
+      - uses: actions/setup-node@v6
+        with:
+          node-version: 24
+      - name: Fetch frozen Rough.js oracle
+        run: |
+          curl --fail --location --silent --show-error \
+            https://registry.npmjs.org/roughjs/-/roughjs-4.0.4.tgz \
+            --output "$RUNNER_TEMP/roughjs-4.0.4.tgz"
+          mkdir "$RUNNER_TEMP/roughjs-4.0.4"
+          tar -xzf "$RUNNER_TEMP/roughjs-4.0.4.tgz" \
+            -C "$RUNNER_TEMP/roughjs-4.0.4"
+          echo "21f8682b994c6063e9605a19f50a6bd9f3b0901cbff4db2326b3f85308e29b7f  $RUNNER_TEMP/roughjs-4.0.4/package/bundled/rough.js" \
+            | sha256sum --check
+      - name: Test
+        env:
+          ROUGH_GO_ROUGH_JS: ${{ runner.temp }}/roughjs-4.0.4/package/bundled/rough.js
+          ROUGH_GO_DIFFERENTIAL_CALLS: "1000"
+        run: go test ./...
+      - run: go test -race ./...
+      - run: go vet ./...

.gitignore

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+coverage.out
+*.test

LICENSE

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+MIT License
+
+Copyright (c) 2019 Preet Shihn
+Copyright (c) 2026 rough-go contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

NOTICE

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+rough-go is a Go port of Rough.js 4.0.4.
+
+Upstream source:
+  Project: Rough.js
+  Version: 4.0.4
+  Commit: 35302b8f1119ad004b4550f9a4d4162d3d845b0a
+  Repository: https://github.com/rough-stuff/rough
+  License: MIT
+  Copyright (c) 2019 Preet Shihn
+
+Compatibility is measured against the Rough.js bundle embedded by D2, whose
+SHA-256 is 5601a7c6046815613316d882ffbaede24261bfec295e3502ae7539abb1814820.
+The pristine Rough.js 4.0.4 browser bundle has SHA-256
+21f8682b994c6063e9605a19f50a6bd9f3b0901cbff4db2326b3f85308e29b7f.
+
+No Rough.js JavaScript is linked into or executed by rough-go. The Go source is
+a translation and remains available under the MIT license in LICENSE.

PROVENANCE.md

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+# Source provenance
+
+rough-go is a source-shaped Go translation of Rough.js 4.0.4.
+
+| Source | Version / commit | License | Relevant files |
+| --- | --- | --- | --- |
+| Rough.js | 4.0.4 / `35302b8f1119ad004b4550f9a4d4162d3d845b0a` | MIT | `src/core.ts`, `geometry.ts`, `math.ts`, `path.ts`, `renderer.ts`, `generator.ts`, `rough.ts`, `canvas.ts`, `svg.ts`, and `src/fillers/*.ts` |
+
+The pristine npm browser bundle has SHA-256
+`21f8682b994c6063e9605a19f50a6bd9f3b0901cbff4db2326b3f85308e29b7f`.
+The npm tarball has SHA-1 `31db3cc9654e7012a5d5701c6234f7601a14d720`
+and integrity
+`sha512-rXmMGcALUlYIFKBbn9aWuxznPKOtnx9bouVC407/uneUNx0mT/4Mo2Z4TUieoCOT+rWmHnOQqVT1FvoN+L3baA==`.
+
+D2's frozen oracle bundle has SHA-256
+`5601a7c6046815613316d882ffbaede24261bfec295e3502ae7539abb1814820`.
+D2 reformatted and unwrapped the browser bundle, replaced deprecated regular
+expression statics with local matches, and replaced exponentiation syntax with
+`Math.pow`. Its later quoted-string typo correction is behaviorally inert. The
+layout and renderer algorithms remain Rough.js 4.0.4.
+
+Every translated Go source file carries an SPDX MIT identifier and the upstream
+copyright attribution. The complete applicable license is in `LICENSE`.

README.md

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+# rough-go
+
+`rough-go` is a native Go port of [Rough.js](https://roughjs.com/) 4.0.4. It
+creates the same ordered drawing operations and SVG path descriptions without a
+JavaScript runtime.
+
+The compatibility target is the exact Rough.js implementation embedded by D2:
+version 4.0.4 at commit
+`35302b8f1119ad004b4550f9a4d4162d3d845b0a`. Later Rough.js releases have
+behavior-changing renderer and option changes, so they are not the oracle for
+this module.
+
+```go
+package main
+
+import (
+	"fmt"
+
+	rough "github.com/d2lang/rough-go"
+)
+
+func main() {
+	g := rough.NewGenerator(nil)
+	d := g.Rectangle(0, 0, 120, 60, &rough.Options{
+		Fill: rough.String("#f6d32d"),
+		Seed: rough.Float64(1),
+	})
+	for _, path := range g.ToPaths(d) {
+		fmt.Println(path.D)
+	}
+}
+```
+
+The full generator surface is ported: line, rectangle, ellipse, circle, linear
+path, polygon, arc, curve, SVG path, every 4.0.4 fill style, operation
+serialization, and `ToPaths` conversion. Pointer-valued option fields preserve
+the JavaScript distinction between an omitted option and an explicit zero.
+
+## Compatibility tests
+
+The regular suite is pure Go:
+
+```sh
+go test ./...
+go test -race ./...
+go vet ./...
+```
+
+The optional differential suite runs the Go port against a frozen Rough.js
+4.0.4 browser bundle. Node.js is used only by the test oracle; the library has
+no JavaScript dependency.
+
+```sh
+ROUGH_GO_ROUGH_JS=/absolute/path/to/rough-4.0.4.js go test ./...
+```
+
+Rough.js 4.0.4 did not ship automated tests. Accordingly, rough-go uses
+source-shaped unit tests, deterministic randomized differential tests, and D2's
+existing exact sketch SVG goldens.
+
+## License
+
+MIT. See [LICENSE](LICENSE) and [NOTICE](NOTICE).