Completes the entry point: the File menu gains a "new from template"
row that opens the centre, and a chosen card becomes a document.
The template loads through `load_editor_state_from_source` — the same
loader a real file goes through — so a document that parses as JSON but
fails schema conversion cannot reach a user as a click that does
nothing. A test runs all four shipped templates through it.
It opens UNSAVED with no bound path, like File > New rather than File >
Open. The shipped `.op` is read-only content; binding it as the save
target would let the first Cmd+S overwrite the template for everyone who
used it afterwards.
Loading happens in the frame drain rather than the press handler because
replacing the document has to re-run the collaboration gate, which the
panel press — which only opens a panel — correctly did not.
Native wiring mirrors the Prompt Center's tiers: paint in the floating
panel pass, press above it in the overlay ladder, hover reporting
`owns_point` so canvas hover is suppressed underneath, scroll swallowed
by the grid, and Escape closing the panel ahead of selection.
File-menu row indices shift by one below the new row; the row-map tests
move with them. One of them asserts a hover value is passed through
verbatim rather than a row meaning, so its number stays put.
Claude-Session: https://claude.ai/code/session_01FqKQqNj8exYwopGDpYUU7x
9ab4715ce1