fix(remote-ssh): disambiguate NUL escapes in the container stat test

[bobleer]

Summary

cargo clippy -p bitfun-services-integrations --features remote-ssh-concrete --all-targets failed with three deny-level clippy::octal_escapes errors, all on one line in the #[cfg(test)] module of remote_ssh/manager.rs.

The parse_container_file_output fixture separated its NUL-delimited fields with \0, which made \00, \01720000000, and \0644 look like possibly-mistaken octal escapes. \0 is always NUL in Rust, so the parsed values were already what the test intended — clippy simply cannot tell that apart from a typo.

The separators are now spelled \x00. Since \x consumes exactly two hex digits, the digits that follow can no longer be read as part of the escape.

Type and Areas

Type: bug fix (lint failure)

Areas: Rust core (services-integrations, remote SSH)

Motivation / Impact

No direct user-facing change, and no behavior change at all: the string is byte-for-byte identical, so the test asserts on exactly the same parsed entry.

The value is unblocking --all-targets clippy. Because the offending literal sits in a #[cfg(test)] module, it is invisible to CI's Rust Build Check, so anyone running the fuller clippy invocation locally hits three hard errors that have nothing to do with their own work. This is pre-existing on main rather than a regression from recent work.

For the record, the field layout is unchanged — 6 NUL-separated fields plus a trailing NUL that parse_container_file_output pops:

field	value
name	pipe
path	/workspace/pipe
kind	o (not d/f/l, which is the point of the test)
size	0
modified	1720000000
permissions	644

Verification

Both run on this branch, rebased on current main:

• cargo clippy -p bitfun-services-integrations --features remote-ssh-concrete --all-targets — exits 0, zero octal_escapes occurrences in the output. Two pre-existing warnings remain and are untouched by this PR: unnecessary_unwrap at remote_ssh/manager.rs:3033 and field_reassign_with_default at remote_ssh/remote_fs.rs:598.
• cargo test -p bitfun-services-integrations --lib --features remote-ssh-concrete — 119 passed, 0 failed, 1 ignored, including container_special_files_are_not_reported_as_regular_files.
• rustfmt --check on the touched file — clean.

Reviewer Notes

The multi-line wrapping of the call is rustfmt's own output for the longer literal, not a hand-chosen style.

One thing worth flagging separately: cargo fmt -p bitfun-services-integrations currently reformats nine other files in this crate, meaning the crate is not rustfmt-clean on main. I deliberately kept those out of this PR to keep the diff focused, so this branch touches only manager.rs. Happy to open a separate formatting-only PR if that is wanted.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable. (n/a — test-only change)