* perf: avoid repeatedly encoding retained VM recipe output
* perf: capture retained VM recipe output as raw bytes in the shared byte buffer
The previous commit added a third byte-retention buffer to the repo. This
replaces it with the one that already existed and removes the remaining
encoding work.
`runRecipeCommand` no longer calls `setEncoding('utf8')` on the child's stdout
and stderr. It keeps the raw `Buffer` chunks and runs one `StringDecoder` per
stream to feed the existing string callbacks, which is exactly how
`setEncoding` is implemented, so callbacks see the same characters at the same
boundaries. With the bytes already in hand the capture encodes nothing: the
4,194,304 bytes the ring still encoded for 4 MiB of output drop to 0, and the
UTF-8 continuation trim collapses from one scan per chunk to a single scan when
the tail is decoded.
Retention is now `GrowingByteBuffer.appendRetainedSuffix`, which had no
production consumer. It gained an O(1) head offset, so `discardPrefix` and
`retainSuffix` mark bytes dead instead of moving the whole tail and `append`
slides or grows only when the head offset runs out of room. Quick Open path
accumulation and the SOCKS handshake buffer get that win too. Without the
offset the per-chunk memmove costs 12.36 ms for 4 MiB; with it, 0.25 ms against
the ring's 0.53 ms and the old per-chunk re-encode's 265.78 ms.
Two behaviour notes. Odd capture limits are clamped once at entry instead of
carrying a per-chunk coercion path no production caller could reach, so an
infinite or NaN cap is now bounded at 1 MiB rather than retaining everything.
And malformed UTF-8 yields a different tail: replacement characters no longer
inflate the byte count, so a malformed tail keeps more of what the recipe
actually wrote.
The encoding-budget assertions no longer spy on `Buffer` itself, where any
unrelated allocation in the same tick could flip them. They count bytes through
the capture's own buffer class and still assert the deterministic oracle: at
most 5 MiB moved for 4 MiB of output, exactly 4 MiB appended, 1 MiB decoded,
and the stored chunks identical to the Buffers the stream delivered.
Co-Authored-By: Claude <noreply@anthropic.com>
* test(vm-recipe): emit Buffers from the doctor stream doubles
Dropping setEncoding('utf8') means stdout and stderr now deliver Buffers, so
the hand-rolled EventEmitter doubles emitting strings threw inside the data
listener — the capture retained nothing and the exit path never settled.
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Co-authored-by: Claude <noreply@anthropic.com>
NeilandClaude
21170c6e22