[danbugs]

Fixes to the guest's files, console and calls, found running hluk once per command and reading what comes back. The kernel side is on plat-hyperlight-v2; its generic fixes (vfscore, ukconsole, ukprint, posix-tty) were reproduced and checked on stock QEMU/KVM, where the console changes leave the output unchanged.

• Mounted files: stat gives the host's mode bits and times, and os.utime sets times. An FsBackend reports times through FileStat::times and sets them through set_times, ignored by default.
• Paths: mkdir -p, the working directory at a mount's root, and mount paths with trailing slashes work.
• The kernel's messages are Hyperlight's guest log (target hyperlight_guest, with library, file and line) instead of the program's stderr, so a failed exec no longer adds ERR: lines to its output. SandboxBuilder::guest_log_level sets the level, --log-level shows them, and the CLI still prints them when hluk itself fails.
• The console is a terminal only where the output reaches one, so isatty, prompts and echo behave as on Linux; drivers keep stdout line-buffered.
• Guest function calls carry up to 1 MiB, from about 72 KB; a larger one fails with Error::CallTooLarge before it is sent.
• The exec driver says why it cannot run a program, and dispatch callback failed is printed only for the driver's own failure.

[Copilot]

🔵 Needs a closer look

The cross-platform host–kernel protocol, transport, and snapshot-sensitive console changes warrant human review of companion-kernel integration results.

No open issues 🎉

What changed in this PR

Updates Hyperlight–Unikraft’s host support and runtime drivers to improve mounted-file behavior, console handling, guest logging, and call capacity alongside the companion kernel changes.

Changes:

• Adds mounted-file timestamps and host permission bits, strips setuid/setgid from chmod requests, and normalizes mount paths.
• Separates kernel logs from program output, adjusts terminal detection and buffering, and improves execution diagnostics.
• Expands guest calls to roughly 1 MiB with early size checks, updates snapshot compatibility, and adds regression coverage.

File	Description
tests/​quickjs.rs	Updates oversized-result test limits.
tests/​python.rs	Covers filesystem, console, large-call, and failure-output behavior.
tests/​project.rs	Clarifies piped REPL behavior in comments.
tests/​compiled.rs	Tests diagnostics for unexecutable files.
tests/​common/​mod.rs	Adds a guest-log capture helper.
tests/​bash.rs	Tests guest logging, encoding, and disabled logging.
templates/​bash-repl/​repl.sh	Shows prompts only for terminal input.
src/​main.rs	Configures guest logging, retains failure diagnostics, and explains oversized scripts.
src/​lib.rs	Expands transport capacity and adds console and logging controls.
src/​hostfs.rs	Exposes host metadata and supports safe permission and timestamp updates.
src/​cli/​mod.rs	Configures terminal behavior around warm snapshots.
src/​cli/​cpio.rs	Checks kernel diagnostics through guest logs.
integrations/​smolagents/​src/​smolagents_hyperlight/​executor.py	Clarifies legacy console behavior in comments.
integrations/​clickhouse/​src/​function.rs	Clarifies legacy driver diagnostics in comments.
integrations/​clickhouse/​Cargo.lock	Locks the filesystem extension dependency.
drivers/​hl_py.h	Keeps Python stdout line-buffered.
drivers/​hl_execdriver.c	Reports execution errors with appropriate status codes.
drivers/​hl_driver.h	Enables line buffering and limits driver-failure messages.
docs/​fs.md	Documents metadata and timestamp support.
docs/​driver.md	Updates the documented call-buffer capacity.
docs/​calls.md	Documents console, logging, and transport behavior.
CHANGELOG.md	Records behavior changes and compatibility implications.
Cargo.toml	Adds filesystem extensions and test logging support.
Cargo.lock	Locks the new filesystem dependency.
build.rs	Bumps the snapshot compatibility contract.
.github/​actions/​arm64-host/​action.yml	Restores executable permissions on downloaded test binaries.

_{Review effort: Balanced}