feat(cli,playground,docs,generators): Export LikeC4 views to Draw.io

Summary

This PR adds export of LikeC4 views to Draw.io (.drawio) format. Users can export from the CLI (likec4 export drawio) and from the Playground (right-click on diagram → DrawIO → Export view / Export all). This allows editing diagrams in Draw.io and reusing them in tools that support the format.

This PR does not include import. Import from Draw.io will be proposed in a separate PR after this one is merged.

What's in this PR

1. Generators (@likec4/generators)

• packages/generators/src/drawio/generate-drawio.ts — Exports a single view or multiple views to Draw.io XML. Maps LikeC4 elements (title, description, shape, color, relationships, etc.) to mxCell vertices/edges. Supports optional layoutOverride, strokeColorByNodeId, strokeWidthByNodeId, edgeWaypoints, and compressed.
• packages/generators/src/drawio/parse-drawio.ts — Used only for round-trip comment parsing (parseDrawioRoundtripComments): when re-exporting after a future import, layout and waypoints from comment blocks in .c4 source can be applied. No import UI or CLI in this PR.
• packages/generators/src/drawio/index.ts — Public API: generateDrawio, generateDrawioMulti, GenerateDrawioOptions, plus getAllDiagrams, parseDrawioRoundtripComments, parseDrawioToLikeC4, parseDrawioToLikeC4Multi (for roundtrip and for the future import PR).
• Tests: generate-drawio.spec.ts, parse-drawio.spec.ts; snapshots in __snapshots__/.

2. CLI (@likec4/likec4)

• packages/likec4/src/cli/export/drawio/handler.ts — likec4 export drawio [path] with options: --outdir, -o, --all-in-one, --roundtrip, --uncompressed, --project, --use-dot.
• packages/likec4/src/cli/export/index.ts — Registers the drawio export command.

3. Playground

• DrawIO context menu export only: DrawioContextMenuProvider, DrawioContextMenuDropdown (Export view…, Export all…), useDrawioContextMenuActions (handleExport, handleExportAllViews; uses generateDrawio/generateDrawioMulti and parseDrawioRoundtripComments). DrawioContextMenu, drawio-events (DRAWIO_EXPORT_EVENT). No Import item or file input in this PR.
• Monaco: only Export to DrawIO action in editor context menu (no Import action). Integration in LanguageClientSync and routes as needed for export.

Playground exports are uncompressed by default so files open reliably in Draw.io desktop.

4. Documentation

• apps/docs/src/content/docs/tooling/drawio.mdx — Export only: mapping (LikeC4 → Draw.io), options, not preserved, multi-diagram, troubleshooting, re-export using comment blocks. No import sections.
• apps/docs/src/content/docs/tooling/cli.mdx — Export to DrawIO section only; no Import from DrawIO section. Intro mentions Export to DrawIO only.

5. Tests

• packages/likec4/src/drawio-demo-export-import.spec.ts — Export tests only; import/vice-versa test skipped in this PR.
• packages/likec4/src/drawio-tutorial-export-import.spec.ts — Export tests only; import and round-trip tests skipped in this PR.
• e2e/tests/drawio-playground.spec.ts — Asserts DrawIO menu shows Export to DrawIO (and Export all). No Import assertion. Run with playwright.playground.config.ts (playground on 5174); main e2e config ignores this test.

What's not in this PR

• No likec4 import drawio command (no packages/likec4/src/cli/import/).
• No Playground "Import from DrawIO" menu item, file input, or Monaco Import action.
• No docs for importing from Draw.io.
• Import/round-trip tests in likec4 specs are skipped; enabled in the import PR.

Post-review fixes (CodeRabbit)

Addresses CodeRabbit AI review (actionable + nitpicks):

Actionable

• parse-drawio.ts: stripHtml now uses shared decodeXmlEntities() (covers ' and all five XML entities). UserObject id in constructed mxCell tag is escaped with escapeXml(userObjId). collectRoundtripForState consolidated to a single pass over idToFqn where possible.
• drawio handler: Explicit guard when --all-in-one and zero views: warn and throw ERR_NO_VIEWS_EXPORTED. ensureSingleProject() only called when no --project is provided, so multi-project workspaces can use --project.
• json handler: languageServices created with await using so it is disposed on exit (file watchers/RPC cleaned up).
• png handler: startTakeScreenshot moved inside the per-project loop so timing reported is per-project, not cumulative.

Nitpicks / cleanup

• useWorkspaceId.ts: Removed commented-out code and unused extensionContext import.
• documentation-provider.ts: Added exhaustiveness check (const _exhaustive: never = node) so new node types require a handler.
• log: configureLogtape now uses explicit generics instead of any; typo fix gerErrorFromLogRecord → getErrorFromLogRecord.
• DrawioContextMenuProvider: Typed EMPTY_DRAWIO_SNAPSHOT; stable getSourceContent via ref to avoid churn on every snapshot.
• useDrawioContextMenuActions: Download uses detached anchor (no appendChild/removeChild); dev-only console.warn when a view is skipped in fillFromModelView.
• generate-drawio.ts: Optional modified?: string in GenerateDrawioOptions and wrapInMxFile for deterministic output (tests/caching).

Second batch (CodeRabbit follow-up)

• parse-drawio.ts: getDecodedStyle and decodeRootStyleField wrap decodeURIComponent in try/catch so malformed percent-encoding (e.g. %ZZ) does not abort parsing; on error return raw string (or undefined/empty). Ternary titlePart clarified with parentheses: (desc || tech) ? ....
• log (index.ts): Destructure config to exclude sinks/loggers from spread (...restConfig) so overrides are not misleading.
• log (formatters.ts): Typo errorMessge → errorMessage in appendErrorToMessage; removed commented-out line.
• DrawioContextMenuProvider: filesRef.current = files moved into useEffect([files]) for concurrent-safety.
• drawio handler: exportParams explicitly typed as ExportDrawioParams; single zero-views guard for both all-in-one and per-view modes.
• png handler: Logger prefix aligned with json: createLikeC4Logger('c4:export').
• generate-drawio.ts: Helper buildOptionsFromRoundtrip(viewId, roundtrip, overrides) extracted; buildDrawioExportOptionsForViews parses source once and distributes options (parse-once optimization for many views).

Checklist (contribution guidelines)

• I have read the latest contribution guidelines.
• I have rebased my branch onto main before creating this PR.
• My commit messages follow Conventional Commits (e.g. feat:, docs:).
• I have added/updated tests for export; import tests are skipped in this branch.
• I have run pnpm test and pnpm typecheck (and pnpm test:e2e for e2e); all pass.
• Documentation updated (drawio.mdx and cli.mdx for export only).
• A changeset has been added for user-facing packages if applicable.

Notes for reviewers

• Export: one .drawio file per view by default; --all-in-one for all views as tabs; --roundtrip applies layout/waypoints from comment blocks; --uncompressed for Draw.io desktop compatibility.
• Playground exposes only Export actions in the DrawIO menu.
• Generators: parse-drawio is present for round-trip comments and for the upcoming import PR; no import entrypoints used here.
• E2E: drawio-playground test is excluded from main config (runs only with playground config on port 5174); screenshot diff tolerance and timeouts tuned for CI.

Review context

The original DrawIO bidirectional work (branch feat/drawio-bidirectional-playground) was reviewed upstream in likec4/likec4 PR #2593 — Fix DrawIO CLI docs, refactor context menu, correct XML generation. Review was done by @sraphaz at the request of @davydkov. This export-only PR is a split from that work; feedback from that review has been incorporated where applicable (e.g. CLI docs, context menu structure, XML generation). CodeRabbit AI review comments have been addressed in the “Post-review fixes” section above.

Summary by CodeRabbit

Release Notes

• New Features

  • Added Draw.io export functionality to CLI and Playground, supporting single and multi-view exports with configurable layout, styling, and compression options.

• Bug Fixes

  • Enhanced parsing robustness for Draw.io data and fixed edge/label rendering logic.

• Documentation

  • Updated documentation covering export functionality and architectural mapping guidance.