* perf(terminal): measure stream byte length natively above a code-unit floor
The terminal RPC path counted UTF-8 bytes with a hand-rolled per-code-point scan
that Buffer.byteLength does natively an order of magnitude faster.
Routed through a small module rather than swapping the shared clipboard helper,
which has ~50 renderer call sites and a partial-count contract on the over-limit
path that must not change.
4.4x on an 8KiB batcher push, 4.2x on a 2MiB snapshot scan, 4.0x on the 48KiB
chunk gate, and 1.26-1.33x on the adversarial early-trip shapes where the legacy
scan bails after a third of the string.
The floor is load-bearing, not defensive. Buffer.byteLength has a fixed ~14ns
call cost against a scan iteration of ~1.5ns, so below the measured 8-12 code
unit crossover the native call is a REGRESSION -- 4.2x slower at one code unit,
which is keystroke echo, the most latency-sensitive PTY shape there is. Short
inputs keep the scan verbatim; 16 leaves margin over the crossover so the worst
sub-floor shape stays at parity.
measureTerminalStreamByteLength takes the native count only when
`length * 3 <= stopAfterBytes` proves the limit cannot trip, so the callers'
truncated running total is never replaced by a full count.
Co-authored-by: Orca <help@stably.ai>
* test(terminal): benchmark production byte-length exports
Co-authored-by: Orca <help@stably.ai>
---------
Co-authored-by: Orca <help@stably.ai>
