#73 os/windows: support cmd.exe and git-bash shell strategy variants

[Anonymous]

Originally created by: kumaakh

Currently all Windows SSH members assume PowerShell. Two additional shell strategies should be supported:

• windows-cmdExe — for members running cmd.exe
• windows-gitbash — for members running Git Bash (bash.exe via SSH)

Each variant needs its own OsCommands implementation (or strategy flags within WindowsCommands).

Backlog item [#10] from docs/MCP-BACKLOG.md. Low priority.

[Anonymous]

Originally posted by: kumaakh

Technical direction: The existing WindowsCommands class in src/os/os-commands.ts (or equivalent) should be refactored:

1. Extract a WindowsPowerShellCommands class (current behavior — rename for clarity).
2. Add WindowsCmdCommands — override the commands that differ (e.g. env var syntax %VAR% vs \, command separators & vs ;).
3. Add WindowsGitBashCommands — extends Unix-style commands but accounts for Windows path quirks (drive letter handling in worktrees — see [#91]).
4. Member registration (
   egister_member) / update_member: add shell param accepting powershell (default), cmd, gitbash.
5. getOsCommands() in the strategy layer selects the appropriate class based on the member's registered OS + shell combination.

Low priority but useful for enterprise environments where PowerShell execution policy is locked down. gitbash variant also directly addresses the worktree path issue in [#91].