Register the recent-entries widget in window.openStationWidgets

[juanlentino]

Fixes #59.

OpenStation looks up widget mount callbacks by id in window.openStationWidgets (window.desktopModeWidgets on older Desktop Mode builds). src/widget.ts only exported render, which the IIFE build places at window.allTerrainFormsWidget.render, so the shell never found allterrain-forms/recent and logged a mount failure on every desktop load.

Change

• src/widget.ts registers the existing renderWidget under allterrain-forms/recent. It merges into whichever registry already exists and never replaces it, since other plugins' widgets live in the same object.
• The render export stays, so mountStandalone and anything reading the IIFE global keep working. The registry is a different global from the one the IIFE's final assignment overwrites, so the hand-assignment issue described in the existing comment doesn't apply. That comment is updated to say so.
• assets/js/widget.js and widget.min.js are rebuilt with npm run build:widget.

Verified

• npm run typecheck: clean.
• npm test: 469 passed, 2 skipped.
• Ran the built widget.min.js against a stub window that already held another plugin's widget. Afterward openStationWidgets held both keys (other/w, allterrain-forms/recent), and desktopModeWidgets pointed at the same object.

Not tested in a live OpenStation desktop yet.

[AllTerrainDeveloper]

Thanks, Juan. I checked this against OpenStation’s widget loader: it reads openStationWidgets by widget ID, and this registers the existing mount callback while preserving the other widgets and the standalone export. The CI checks are green. Nice fix.