Rename persisted chart- and dataset-named config keys and widget types on the next config version bump

[mairas]

Context

Time-series visualizations are graphs (see the companion issue for the decision and its rationale). This issue covers the last piece: identifiers that are written into stored dashboard configuration, so renaming them requires a config version bump and a migration.

Do not bump the config version for this alone. The rename is cosmetic and the migration risk is not. Fold it into the next bump made for a reason that justifies one on its own, and treat this issue as the checklist for that bump.

Identifiers to rename

Config keys (src/app/core/interfaces/widgets-interface.ts):

Current	New
datachartPath (:414)	datagraphPath
datachartSource (:416)	datagraphSource
datachartAngleRange (:418)	datagraphAngleRange
showMiniChart (:275)	showMiniGraph
verticalChart (:460)	verticalGraph
datasetAverageArray (:420)	averageArray
showDatasetMinimumValueLine (:432)	showMinimumValueLine
showDatasetMaximumValueLine (:434)	showMaximumValueLine
showDatasetAverageValueLine (:436)	showAverageValueLine
showDatasetAngleAverageValueLine (:438)	showAngleAverageValueLine

The Dataset prefix drops rather than becoming Graph: "dataset" is a KIP concept Skip no longer has (the registry and client-side recorder went away in the v12 upgrade), so the word is being removed, not translated. The companion issue covers the non-persisted half of that removal.

Widget type strings: widget-data-chart → widget-data-graph, widget-windtrends-chart → widget-windtrends-graph. These are component selectors, but the selector doubles as the persisted type field of a stored widget (widgets-interface.ts:67), so they are not free to rename.

Touchpoints

• configuration-upgrade.service.ts — a new version transform following the existing v11..v19 chain, plus two existing tables keyed by the old strings: the path-defaults map ('widget-windtrends-chart', :61) and the legacy class-name map ('WidgetDataChart': 'widget-data-chart', :139).
• src/default-config/config.blank.dashboard.ts — the seeded default dashboard stores the type strings.
• src/assets/skip-dashboard-schema.json — regenerate with npm run gen:mcp-schema; test:mcp-schema gates drift in npm run ci.
• widget.service.ts, dashboard-history-series-sync.service.ts, skip-series-contract.ts, remote-context-demand.util.ts and the corresponding specs all match on the type strings.
• The embed route #/widget/:type (app.routes.ts:60) resolves a widget by selector, and single-widget-host.component.spec.ts asserts that as a cross-package string contract with @halos-org/skip-freeboard-panel. The panel's manifest currently exposes only widget-wind-steer, so no time-series widget crosses that boundary today — but check the manifest again before renaming, not just this repo.

Verification

• A dashboard saved on the previous config version upgrades on load, with every affected widget keeping its configured path, source, angle range and orientation.
• An exported config file from the previous version imports successfully.
• npm run ci passes with the schema artifact regenerated.

Companion issue for the wording and the non-persisted identifiers: #591