feat: add umf.dashboard platform-neutral dashboard profile

[garyfischer-maker]

Summary

Proposes umf.dashboard 0.1.0, a semantic extension that describes a dashboard independently of Databricks AI/BI (Lakeview .lvdash.json) or Tableau (.twb/.twbx). It follows the same pattern as umf.ddd. The goal is to port dashboards between platforms through UMF: native umf.lakeview / umf.tableau extensions keep the exact platform detail, this profile holds the shared meaning, and every import or export reports what didn't translate.

This PR adds only the neutral profile. Importers, exporters and the native extensions would come in follow-up changes.

Vocabulary

Scope	Kind	Content
document	dashboard	title, ordered pages, layout.columns grid, optional theme
module	page	title, role canvas or global-filters
module	data	holds datasets shared across pages
element	dataset	table or query source, grain, fields marked column or measure (measures declare an aggregate expression)
element	visual	chart, dataset reference, channel encodings, rows aggregated/detail, position, optional trace id
element	text	plain or markdown content, position
element	filter	control type, explicit {dataset, field} targets, default, position

Design choices worth reviewing

• Fields are column or measure, not dimension/measure, because a raw numeric column isn't a dimension.
• SQL and Tableau expressions are kept with their language tag and never parsed (DASHBOARD_EXPRESSION_OPAQUE). As with DDD invariants, this marks the document incomplete and blocks the edit API.
• Overlapping layout is a warning rather than an error, because Tableau floating zones are legal.
• Unknown content is retained and reported (DASHBOARD_UNKNOWN). Not modeled in 0.1.0: Tableau parameters and actions, per-visual filter exemptions, cross-filter wiring, permissions.

Changes

• spec/extensions/dashboard/: extension package and payload schema
• src/extensions/dashboard/: semantic validator plus readDashboardDocument, writeDashboardDocument, inspectDashboard, getDashboardDefinition, editDashboardDefinition
• fixtures/dashboard/marketing-campaign.json: built from a deployed Lakeview dashboard
• tests/dashboard/profile.test.ts: US-077-AC1 to AC4, including 28 deliberate-corruption checks
• HELIX: FEAT-026, US-077, CONTRACT-055, TD-077; regenerated acceptance ledger and package/schema audits

Verification (Windows 11, Bun 1.3.14)

• bun test tests/dashboard tests/traceability: 6 pass
• bun run test:schemas: 62/62 packages, 350/350 schemas
• bun run typecheck: clean

Dependencies and open items

• Contains a merge of fix: make line endings and repository paths platform-independent on Windows #12 (Windows line endings and paths). Merge fix: make line endings and repository paths platform-independent on Windows #12 first, and this diff reduces to the dashboard commit.
• Draft because there is no browser test coverage yet (US-077-AC5, mirroring DDD's dddRoundTrip). A Lakeview round trip of the fixture's source dashboard is also planned before this is marked ready.

🤖 Generated with Claude Code

[easel]

Off hand this looks incredible!