[emaarco]

Summary

The SVG renderer only draws SVG, yet it lived in src/domain/views/render/, and two file adapters (FileImageWriter, PngRenderer) called it directly. This PR makes it a browser-safe driven adapter behind an outbound port, with byte-identical output.

• New port and adapter: application/port/out/RenderDiagramPort is implemented by adapters/out/render/SvgRenderer. The renderer is grouped by step: crop/ (which part of the plane), paint/ (shapes, connections, labels), compose/ (frame, scale, badges, tiles); DocRenderer and types.ts stay on top. SvgRenderer carries a comment on why this is custom code instead of bpmn-js.
• In-memory layout moves to the domain: domain/views/DrawableDoc parses the XML and lays out a file without a diagram (its own problems and the two notes, word for word). RenderSvgService and RenderDiagramService call it, then the port.
• Image writing gets the finished drawing: WriteImagePort.ImageRequest carries drawn: RenderResult instead of XML and options, so out/files no longer imports the renderer. PngRenderer.render(drawn) only rasterises; the RENDER_MAX_SIZE default moved to renderPng in node.ts (the CLI always passes maxSize).
• Public types: RenderOptions, RenderResult, RenderProblem, RenderTile, RenderHighlight, RENDER_MAX_SIZE, MIN_LABEL_SCALE and HALO_COLORS now live in port/in/RenderSvgUseCase.ts. The exports of index.ts and node.ts keep their names and signatures.
• Architecture test: out/render is a registered adapter; new checks that no domain file contains <svg / <g and that adapters/out/render imports no node:*. The three render constants left the list of values re-exported from the domain.
• Docs: CONTRIBUTING.md layout table, the diagram in docs/architecture.md, test paths in docs/testing.md. The render tests moved to test/adapters/out/render/.

Verification:

• vitest run: 2395 passed, 246 skipped.
• Byte-identical output: 36 outputs of bpmn render (SVG, PNG and the --json reports) saved before the change and compared with cmp after it, covering several planes, --problems, --tiles, --highlight, files without a diagram and tools/scenarios. No difference.
• npm run build, biome lint, knip, knip --production --exclude dependencies, jscpd and tools/iso/check.mjs pass. The bench regression gate and the fuzz run of npm run gate were not run locally.
• No command, option or output changed, so guide.ts needs no update.

Checklist

• npm run typecheck passes
• npm run gate passes
• src/report/guide.ts and the matching page in docs/ are updated (only if a command, option or output changed)
• PR title is a changelog-worthy Conventional-Commit summary

Linked issue

Closes #113