* perf(runtime): gate terminal.list visual layouts and stop the false writable claim
visualLayouts is ~31% of a large terminal.list payload (44,208 B of 137,412 B on a live 134-terminal remote runtime) and has exactly one consumer: the human-readable CLI formatter. Gate it behind an includeVisualLayouts request param that defaults to included, so pre-flag clients are unaffected, and have every --json/internal caller opt out.
Also drop the record-backed builder's writable, which was a verbatim copy of connected. terminal.show now states writability explicitly as exactly what terminal.send's PTY gate enforces.
* test(runtime): type the payload-size fixture arrays for tsc
* fix(runtime): preserve terminal list compatibility
* test(runtime): guard terminal list optimization
* fix(cli): preserve agent access to terminal layouts
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