tty: add raw-vt and io raw modes

[samuel-williams-shopify]

Adds string raw-mode selection to tty.ReadStream#setRawMode():

• setRawMode(true) keeps the existing behavior.
• setRawMode('raw') explicitly selects the existing Node raw mode, backed by libuv UV_TTY_MODE_RAW_VT.
• setRawMode('io') selects libuv UV_TTY_MODE_IO for binary-safe I/O mode on Unix.
• readStream.rawMode exposes the exact current mode while readStream.isRaw remains boolean for compatibility.
• Unknown string modes are rejected.

This is intended to address the output-processing distinction discussed in #63059 and follows libuv's existing UV_TTY_MODE_IO semantics. It preserves the current setRawMode(true) behavior instead of changing it.

Related libuv hardening PR: libuv/libuv#5174

Refs: #63059
Refs: libuv/libuv#32

Local verification:

• git diff --check passes.
• A full local build could not complete because macOS killed Cargo build-script-build executables as untrusted on this machine; relying on CI for the native build and pseudo-tty test run.

[addaleax]

I would not use 'raw-vt' as a name and instead just use 'raw'. UV_TTY_MODE_RAW_VT is what UV_TTY_MODE_RAW should probably have been all along – the only reason they aren't merged (yet) into a single constant is backwards compatibility expectations in libuv.

[samuel-williams-shopify]

Agreed, updated.

[samuel-williams-shopify]

Related libuv hardening PR: libuv/libuv#5174

That PR makes Unix uv_tty_set_mode() return UV_EINVAL for unrecognized uv_tty_mode_t values, matching the existing Windows behavior.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74448/

[samuel-williams-shopify]

I can't see the CI failures, it says access denied.

[addaleax]

@samuel-williams-shopify The failures seem exclusively related to alpine:

  ...
 length differs.
expect=4
actual=7
patterns:
pattern = ^raw=true$
pattern = ^normal=false$
pattern = ^raw\-string=true$
pattern = ^io=false$
outlines:
outline = stty: standard input: Not a tty
outline = raw=true
outline = normal=false
outline = stty: standard input: Not a tty
outline = raw-string=true
outline = stty: standard input: Not a tty
outline = io=false
not ok 5141 pseudo-tty/test-set-raw-mode-modes
  ---
  duration_ms: 287.86900
  severity: fail
  stack: |-
    stty: standard input: Not a tty
    raw=true
    normal=false
    stty: standard input: Not a tty
    raw-string=true
    stty: standard input: Not a tty
    io=false
  ...

Not sure what's different on the Alpine runners, I guess if there's no obvious reason for this it might be fine to silence stderr for stty instead of specifying inherit there