feat(migrate): lay out migrated views from an MTIP export with -layout

[devin-ai-integration]

What and why

sysml <model>.mdzip -convert sysml -layout <mtip-export.xml> lays out the views a SysML v1 migration writes from the diagram geometry an MTIP (HUDS XML) export of the same project records. The XMI carries no diagram geometry, so migrated views were auto-laid-out and the arrangement an engineer settled on was lost; the export holds exactly that layer. It is read as an augment, never as a second model input: the .mdzip/.xmi stays the one source of structure and behavior.

• New package internal/translate/mtip: a streaming encoding/xml reader that keeps the packet's metadata and its diagram records (those with relationships/element or relationships/diagramConnector) and ignores every model record. Placements are transformed on read — Cameo stores y negated, so x = left, y = -top, width = right - left, height = top - bottom gives y-down pixels from the top left; negative values are written as-is. Connector waypoints are emitted source to target: clientPoint, breakpoints reversed, supplierPoint. Malformed placements/connectors are recorded per record, not fatal; unknown relationship_metadata tags (colors, fonts, images) are counted by tag and dropped.
• migrate.Options{Layout, LayoutSource}, MigrateOptions and FromModelOptions; Migrate/FromModel are zero-option wrappers. Diagram records join sysmlv1.Diagram.ID by the record id (the xmi:id). An export with diagram records none of which joins is refused: <layout>: none of its N diagram records matches a diagram of <model>; the layout file was exported from a different project.
• writeView writes, after the expose lines, @DiagramLayout::Canvas { unit = "px"; … } sized by the bounding box of what is written, metadata DiagramLayout::Layout about <ref> { x; y; width; height; } and metadata DiagramLayout::Route about <ref> { points = (…); } — $::DiagramLayout:: where a member shadows the library, like Views::. Geometry is written only for what the view exposes: a placement whose element resolves and whose reference is one of the view's exposes, a route whose connector has an exposable name. Everything else is counted. To make a named connector exposable, written() now treats a named Connector whose ends resolve as a member (an anonymous connect a to b; still is not); this changes no existing golden and the TMT migration without -layout is byte-identical before and after.
• Report: Report.Layout *LayoutSummary (records, joined, unmatched, views without layout, placements/routes written / not exposed / dangling, malformed, unsupported by tag), a ## layout section in the text report, the JSON field, a clause appended to Summary(), each laid-out diagram's own note extended, and an unmapped Layout row per unmatched record (matching no diagram, or a diagram the migration writes no view for), and per malformed record. Joined is counted in the write path, so joined + unmatched always equals the record count; non-finite bounds and a diagram record without <id> are malformed, never written.
• CLI: -layout FILE, validated like -migration-report (XMI/.mdzip input only; may not name the model, -o, the report or the results; requires -convert). convert.Migrate takes migrate.Options; all callers migrated. Usage, the man page, the migration reference (a "Layout from an MTIP export" subsection), the roadmap paragraph and a changelog fragment are updated.

Measured on the OpenMBEE TMT model (TMT.mdzip) with its MTIP export (2022x v1.0.0, Cameo 2022x Refresh2), neither committed:

diagrams 721, joined 721, unmatched 0, views without layout 625 (of 1346)
placements 10374: written 4196, not exposed 6020, dangling 158
routes     4792: written 9,    not exposed 4783, dangling 0
malformed 0, unsupported {}

laid out 721 of 1346 diagrams from TMT_mtip.xml: 4,196 elements positioned, 9 connectors routed. The 625 uncovered views are export scope (Sandbox, profiles, document packages). The exposed-only rule is what leaves 6,020 placements and 4,783 routes unwritten: activity and state nodes, states written inside bodies and table rows have no exposable name — naming them so a view can expose them is the follow-up the roadmap paragraph names, not part of this change.

Specification basis

Presentation only: the DiagramLayout standard library package (docs/project/diagram-layout-annotations.md) already defines Layout, Route and Canvas; this writes them. No row of docs/project/spec-compliance.md moves.

How it was verified

• internal/translate/mtip unit tests: bound transform, route order with 0/1/2 breakpoints and an absent breakPoint, malformed records recorded not fatal, unsupported tags counted, non-diagram records ignored, metadata read, ill-formed XML fails with a position.
• tests/migrate: new layout.xmi + layout.layout.xml pair (BDD and IBD, a shown-but-unexposed element, a dangling id, a connector of an unwritten element, a record matching no diagram, a malformed placement, an unsupported fillColor) with notation and report goldens, analysed clean; the fixture is also pinned without -layout. Byte-identity of MigrateOptions(…, Options{}) against Migrate for every existing fixture; the project-mismatch error; an opt-in tests/migrate/tmt_layout_test.go gate (OPENSYSML_TMT_MDZIP, OPENSYSML_TMT_MTIP) asserting 721 joined, 0 unmatched, 0 malformed, clean analysis — run locally with the pair above.
• cmd/sysml: -layout validation tests beside the -migration-report ones and an end-to-end run on the fixture pair.
• Every existing golden under tests/migrate/testdata/xmi is untouched. go build ./..., go vet ./..., gofmt -l . (empty), go test ./... with the corpus require variables set and the corpora downloaded, make lint, make man-check, python3 scripts/changelog.py check, check-doc-links.py, check-doc-ids.py all pass.

Checklist

• make test and make lint pass locally
• Tests added or updated for the change
• Documentation extended where it already covers the surface (see CONTRIBUTING.md)
• Changelog entry added as changes/unreleased/<slug>.<section>.md, not as an edit to CHANGELOG.md
• baselines regenerated and make docs-counts run if a gate count moved (compliance rows need nothing: the census is counted at docs build)
• No internal work-item labels (waves, slices, F4, K5) in the body, docs, or changelog

[devin-ai-integration]

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