fix(platform): in the Flatpak a pass's shell is bash

Flatpak sets SHELL to /bin/sh, the host's (zsh here) being no file of
the Sdk's, and claude's Bash tool runs commands with bash or zsh. In the
sandbox SHELL becomes /bin/bash unless it names a bash or zsh that is
there. Found by the sandbox checks: a pass's environment had SHELL=/bin/sh.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

interfaces/Crafter.Review-Platform.cppm

@@ -51,6 +51,11 @@ export namespace Crafter::Review::Platform {
     // $HOME), so git reads ~/.config/git/config, Playwright finds
     // ~/.cache/ms-playwright, and claude and npx behave as on the host.
     void RestoreHostXdg();
+    // Flatpak sets SHELL to /bin/sh, the host's (zsh here) being no file of
+    // the Sdk's. claude's Bash tool runs commands with bash or zsh, and the
+    // Sdk has bash: SHELL becomes /bin/bash unless it already names a bash
+    // or zsh that is there.
+    void RestoreShell();
     // The absolute path of the running binary (/proc/self/exe).
     std::filesystem::path SelfExe();