fix: pass windowsHide to the git execSync calls so no console window is created on Windows

[leonvchan]

Fixes #101.

execSync with a string command runs through cmd.exe on Windows, and windowsHide defaults to false, so the child process is created with a console window whenever the caller has no console of its own — which is the case for the OpenCode service process. A newly created console window takes foreground focus, which breaks IME composition while a session is in use.

The CLI entrypoint already passes windowsHide: true, which suggests the omission here is an oversight. stdio: ["pipe", "pipe", "pipe"] does not suppress the window on Windows — only windowsHide does.

This adds windowsHide: true to the six execSync option objects in src/services/tags.ts. No other change.

Measured on Windows 11 (build 26200.8655), OpenCode 2.0.21, plugin 2.0.15

• before: a 60 ms process/window watcher recorded 105 visible ConsoleWindowClass windows in 133 s while a session was active;
• after applying this change to the installed copy and rebooting: 1 visible console window over 153 s, and it occurred during cold npx startup of the MCP servers, not during turns.

Attribution caveat, stated plainly: that capture could not isolate this plugin from other console-window sources (OpenCode's own MCP startup also spawns cmd.exe /d /s /c "npx ...", whose children include node.exe and git-remote-https.exe). This PR therefore rests on the code defect, not on a clean A/B.

Not addressed here

Two things noticed while investigating, left alone to keep this PR minimal:

• getGitRoot() is not memoized (repoInfoCache only covers getGitRepoInfo()), so it shells out to git on every call.
• execSync with a string command also routes through cmd.exe; execFileSync("git", [...]) with an argv array would avoid that extra process layer entirely.