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-tui/src/app/mod.rs

@@ -813,11 +813,11 @@ pub(crate) mod win_native_selection {
             let Ok(saved) = u32::try_from(saved) else {
                 return;
             };
-            if let Some((handle, current)) = stdin_console_mode() {
-                if current != saved {
-                    unsafe {
-                        let _ = SetConsoleMode(handle, saved);
-                    }
+            if let Some((handle, current)) = stdin_console_mode()
+                && current != saved
+            {
+                unsafe {
+                    let _ = SetConsoleMode(handle, saved);
                 }
             }
         }