Keep xmd repl running when History reaches twelve entries #1017

Submitting a twelfth entry at 160×36 should leave xmd repl running, with History and its actions available.

During the #1013 test migration, a running REPL accepted eleven plain-text entries, then ended on the next submission with:

ReplRenderError: the engine placed node-19 at a fractional position
(x=120.0078125, y=34, width=11, height=1)

The stack reaches integral in packages/cli/src/repl/renderer.ts:454 through commitReplFrame in program.ts:3392. The Planner identified this as pre-existing at cleanup base 57065b7f. Closed #875 establishes the whole-cell geometry invariant; this issue owns the newly reproduced failure, without rewriting that completed story.

Reproduce by starting a 160×36 REPL, submitting Entry 1 text. through Entry 12 text. and waiting for each entry to finish before the next submission. The cleanup page-object witness performs exactly that sequence through ordinary terminal input. Its first output records eleven successful entries before the fractional-position error.

Acceptance: twelve and further entries finish without ending the command; the resulting controls use whole-cell bounds and remain reachable. Preserve entry results, History selection and drafts. Add focused regression evidence using the running terminal; do not weaken the renderer’s whole-cell check.