[Weidong Cui (wdcui)]

This PR adds /dev/tty and gives the guest at most one terminal, its controlling terminal, which any standard stream may refer to. The userland broker takes the host controlling terminal only when it is verifiably in the foreground and no standard stream is a pipe or socket; otherwise nothing in the guest is a terminal (isatty false, ENOTTY, /dev/tty ENXIO). Terminal signals reach the initial process group even when no stream refers to the terminal. Tests cover the broker, shim, and runner.

[github-actions]

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

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--- failure enum_variant_added: enum variant added on exhaustive enum ---

Description:
A publicly-visible enum without #[non_exhaustive] has a new variant.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#enum-variant-new
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/enum_variant_added.ron

Failed in:
  variant OpenError:NoSuchDevice in /home/runner/work/litebox/litebox/litebox_broker_core/src/fs/errors.rs:32

--- failure inherent_method_const_removed: pub method is no longer const ---

Description:
A publicly-visible method or associated fn is no longer `const` and can no longer be used in a `const` context.
        ref: https://doc.rust-lang.org/reference/const_eval.html
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/inherent_method_const_removed.ron

Failed in:
  TestStdioProvider::with_terminal in /home/runner/work/litebox/litebox/litebox_broker_core/src/test_support.rs:161

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/inherent_method_missing.ron

Failed in:
  TestStdioProvider::with_uncontrolled_terminal, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_core/src/test_support.rs:177
  TestStdioProvider::terminal_queries, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_core/src/test_support.rs:219
  Resolver::is_terminal, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_core/src/fs/resolver.rs:1190

--- failure trait_method_missing: pub trait method removed or renamed ---

Description:
A trait method is no longer callable, and may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-item-signature
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/trait_method_missing.ron

Failed in:
  method is_terminal of trait Backend, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_core/src/fs/backend.rs:167

--- failure trait_method_parameter_count_changed: pub trait method parameter count changed ---

Description:
A trait method now takes a different number of parameters.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-item-signature
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/trait_method_parameter_count_changed.ron

Failed in:
  StdioProvider::terminal now takes 0 instead of 1 parameters, in file /home/runner/work/litebox/litebox/litebox_broker_core/src/stdio.rs:74

--- failure function_missing: pub fn removed or renamed ---

Description:
A publicly-visible function cannot be imported by its prior path. A `pub use` may have been removed, or the function itself may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/function_missing.ron

Failed in:
  function litebox_broker_platform_linux_userland::terminal::open_stdio_terminals, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_platform_linux_userland/src/terminal.rs:35

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/inherent_method_missing.ron

Failed in:
  LinuxTerminal::open, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_platform_linux_userland/src/terminal.rs:111

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/inherent_method_missing.ron

Failed in:
  UserlandStdioProvider::open_terminals, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_userland/src/stdio.rs:64
  UserlandStdioProvider::with_terminals, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_userland/src/stdio.rs:85
  UserlandStdioProvider::close_terminals, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/e22be73d3e3f123e979679dd25821f152572be5e/litebox_broker_userland/src/stdio.rs:113