fix(cua-driver): keep Windows autostart on the junction path

[rsyuzyov]

Summary

• stop canonicalising the executable path on Windows when registering autostart
• retain the invoked bin -> current -> releases/<version> junction path so upgrades can retarget current without rewriting the Scheduled Task
• keep best-effort canonicalisation on non-Windows platforms
• preserve extended UNC and long-path forms while simplifying short extended drive-letter paths
• add focused normalization tests plus a native Windows installer/Scheduled Task regression

Addresses #2137.

Why

The Windows installer exposes cua-driver.exe through two directory junctions:

bin -> packages/current -> packages/releases/<version>

Canonicalising the executable path before registration resolves that chain to a versioned release path. The Scheduled Task is then pinned to the old release when an upgrade retargets current.

On Windows this change stores the executable path returned for the invoked junction path without calling canonicalize. Directly invoking a versioned executable still registers that exact versioned path.

Native Windows result

Windows preserves the invoked path here. A test executable launched through the production-shaped two-junction chain reported the visible bin path from the same current_exe_for_autostart() function used for task registration; it did not report the canonical release path.

The end-to-end Scheduled Task regression then:

1. installed a real source-built cua-driver.exe behind bin -> current -> probe-v1;
2. ran autostart enable through bin and verified the task action retained that visible path;
3. retargeted current to a separately built probe-v2 executable without modifying the task;
4. started the task and verified probe-v2 executed and reported its version marker.

This proves both the Windows current_exe() premise and the actual Task Scheduler upgrade behavior. The next-version fixture is synthetic so the regression is deterministic; the same run separately passed the released installer/reinstall migration smoke and the source-built local install/daemon smoke.

Validation

Final head: 0cc94db92bab723e929a8428c486a17ab76f339a
Base: 32f0ef8537c503918116ab7d4cc4c1c262c50870

• E2E: Rust Windows interactive run 30969836896, exact requested source SHA 0cc94db92bab723e929a8428c486a17ab76f339a: passed
  • native autostart unit slice: 9 passed, including the two-junction current_exe_for_autostart() case
  • real Scheduled Task junction-retarget regression: passed
  • released install and legacy migration: passed
  • isolated local install and daemon get_config: passed; source_sha was 0cc94db92bab723e929a8428c486a17ab76f339a, version 0.17.0
• rust-windows-install-local artifact 8916283387:
  • config SHA-256 d22e3bd98c6ec45fc7d3077301b30cb628c602f941e9291ead0c63f6c270f406
  • version SHA-256 4bd6213fdbfebac8985b2e541b0dd0bc52a823c9b71a4db88dcae2e9db4942e4
  • release install SHA-256 05c732d9cceacfaac027a2c7dce72b99354f70a1cb9419e9aeae306611cfd58c
  • reinstall SHA-256 ba6f86b65206c63124369c928b024b84044f3b3734ca4ce877d8a0f6173897fb
• local focused autostart slice on macOS: 7 passed; Windows-only cases were certified in the exact-head run above

Contributor attribution is preserved across the rebase: Roman Syuzyov remains author of all three contributed commits.

[Copilot]

Pull request overview

Updates Windows autostart registration so the Scheduled Task stores the junction path to cua-driver.exe (rather than a canonicalized, version-pinned release path), ensuring upgrades that flip current are picked up automatically. This aligns the implementation with the intended Windows upgrade behavior described in #2137.

Changes:

• On Windows, stop canonicalizing std::env::current_exe() when computing the autostart executable path (preserves the junction chain).
• Keep canonicalization on non-Windows platforms to resolve symlink chains.
• Expand/update documentation around why Windows must not canonicalize this path.

Suppressed comments (1)

libs/cua-driver/rust/crates/cua-driver/src/autostart.rs:163

• On Windows, stripping the \\?\ extended-length prefix unconditionally can change semantics for UNC paths (\\?\UNC\server\share\...) and can break long paths where the prefix is required to exceed MAX_PATH. Since the comment says this is for readability, it should only strip in the safe \\?\C:\... case (and ideally only when the unprefixed path is short enough).

    #[cfg(target_os = "windows")]
    let path = path
        .strip_prefix(r"\\?\")
        .map(str::to_owned)
        .unwrap_or(path);

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[f-trycua]

Reviewed final two-file diff at 0cc94db. Exact Windows installer/Scheduled Task run 30969836896 passed the invoked-junction premise, real current-retarget launch, released migration, and source-provenance smoke; all repository checks pass and contributor attribution is preserved.