[Bug]: Unused/dead-code warnings for all 8 Linux-only symbols in CLI self_update module on Windows builds

[1688mengdie]

Summary

The upstream CI logs for main report a cluster of unused/dead-code warnings in the CLI self-update module. Evidence from GitHub Actions run 33035362609 (job "CLI Tests (windows-latest)"; the same entries repeat across runs 33050974141 and 33047041028):

• warning: unused import: flate2::read::GzDecoder --> src/apps/cli/src/self_update.rs:2:5
• warning: unused import: std::io::Cursor --> src/apps/cli/src/self_update.rs:8:5
• warning: unused import: tar::Archive --> src/apps/cli/src/self_update.rs:12:5
• warning: constant DEPRECATION_WARNING is never used --> src/apps/cli/src/self_update.rs:18:7
• warning: function find_package_dir is never used --> src/apps/cli/src/self_update.rs:1166:4
• warning: function validate_entrypoint_pair is never used --> src/apps/cli/src/self_update.rs:1178:4
• warning: function validate_plugin_host_resources is never used --> src/apps/cli/src/self_update.rs:1201:4
• warning: function copy_plugin_host_resources is never used --> src/apps/cli/src/self_update.rs:1214:4

The module only performs a real installation on Linux: install_archive (the consumer of all eight symbols) is behind #[cfg(unix)], and a #[cfg(not(unix))] stub twin exists. On non-Unix builds (Windows compiles the whole module) rustc therefore reports all eight symbols as unused/dead.

Root Cause Analysis

• The eight symbols are declared unconditionally but their only consumers live inside the #[cfg(unix)] install path (install_archive and the validation/upgrade chain reachable only from it).
• On Windows builds the Unix install path is compiled out, so rustc flags the imports/const as unused imports and the functions as dead code. The warnings are structural, not flaky: the same entries appear in every full CI run of main (runs 33035362609 / 33050974141 / 33047041028 all reproduce them).

Proposed Fix

Gate exactly these eight declarations with #[cfg(unix)] (imports at lines 2/8/12, the DEPRECATION_WARNING const, and the four helper functions), so:

• Windows/non-Unix builds stop emitting the warnings;
• the Linux install path is unchanged (all eight symbols stay available exactly where they are consumed).

No #[allow(dead_code)]/#[allow(unused_imports)] suppression is involved; the warnings are eliminated by precise cfg gating.