chore(gates): finish the Windows sweep — zero clippy findings workspace-wide

Second layer of platform gaps the mac/linux-only gate history left:
unix-only test imports/helpers now cfg-gated (mermaid, fast-worktree,
hunk-tracker, pager-render link test, three pty_e2e module decls),
clippy-suggested cleanups in Windows-cfg code (file-utils classifier,
tui console-mode restore, shared clipboard arboard-error flow, tools
terminal closure, workspace capability tail), and `cargo update` of h2
(RUSTSEC-2026-0258) and webbrowser (RUSTSEC-2026-0257) so `cargo deny
check advisories` passes again.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KSy9S31pZNWXtRZNVJ1sDf

crates/codegen/kigi-file-utils/src/workspace_classifier.rs

@@ -89,10 +89,10 @@ fn is_platform_system_dir(cwd: &Path) -> bool {
 
 #[cfg(target_os = "windows")]
 fn is_platform_system_dir(cwd: &Path) -> bool {
-    if let Ok(temp) = std::env::var("TEMP").or_else(|_| std::env::var("TMP")) {
-        if cwd.starts_with(&temp) {
-            return true;
-        }
+    if let Ok(temp) = std::env::var("TEMP").or_else(|_| std::env::var("TMP"))
+        && cwd.starts_with(&temp)
+    {
+        return true;
     }
 
     let path_lower = cwd.to_string_lossy().to_lowercase();
@@ -103,7 +103,7 @@ fn is_platform_system_dir(cwd: &Path) -> bool {
         return true;
     }
 
-    if cwd.parent().map_or(false, |p| p.parent().is_none()) && cwd.to_string_lossy().len() <= 3 {
+    if cwd.parent().is_some_and(|p| p.parent().is_none()) && cwd.to_string_lossy().len() <= 3 {
         return true;
     }