The last six hand-rolled dialogs become Dialog

[WaylandYang]

Closes #384.

The five hand-rolled dialogs in the library (extraction drops, error text, ingest token, new source, source settings) and the one in Settings (new knowledge base) are now Dialog. Bodies unchanged; each lost its own scrim, panel, header, close cross, footer strip, Escape listener and scrim mouse-down check, and gained what Radix gives every Dialog: focus trapped inside, role="dialog" with a title and description, Escape and scrim click that close it, and the near-solid u-modal-panel skin instead of glass. Titles, descriptions and footers moved into the component's slots; the ingest-token title keeps its key icon; the source-settings dialog's delete confirmation stays nested and Radix's layering lets only the top one answer Escape. Widths come off the three-step scale — sm for the new base, md for the rest.

Verified in the browser: New source opens as a 512 px role="dialog" with all twelve kinds and closes on Escape; New knowledge base opens at 384 px with its inputs and pack cards and closes on Escape and on a scrim click. pnpm build passes; no u-modal-scrim is left in a page.

🤖 Generated with Claude Code