fix(windows): centralize subprocess compat, add safe_split_command, secure_file_chmod, master_subprocess_run

[dellastreet53-dev]

Adds a comprehensive Windows subprocess compatibility module with:

• safe_split_command: shlex.split replacement that preserves backslashes on Windows
• secure_file_chmod: cross-platform chmod (ICACLS on Windows, os.chmod on POSIX)
• master_subprocess_run/master_subprocess_popen: centralized .cmd shim resolution
• safe_subprocess_run: convenience wrapper for string commands
• windows_detach_popen_kwargs: correct detached-process creation flags

Migrates 31 files from raw shlex.split (backslash destruction on Windows),
os.chmod (ineffective on Windows), and Path.home()/.hermes (breaks profiles)
to the centralized wrapper.

[teknium1]

Thanks for the broad Windows portability audit. The underlying problem is still real on current main: agent/shell_hooks.py:451 parses commands before the shell=False spawn at agent/shell_hooks.py:462-469, and agent/copilot_acp_client.py:70-74 constructs ACP argv from shlex.split.

Problems

• In a2cbfbda48e3, safe_split_command() returns [command] on Windows, but the migrated shell-hook caller still uses shell=False. A command with arguments therefore becomes one executable name instead of an argv vector.
• plugins/disk-cleanup/__init__.py calls safe_split_command(cmd, posix=True), while the new helper accepts no posix keyword; this raises TypeError.
• master_subprocess_run / master_subprocess_popen pass the entire remainder of a string Node command as one argument, so npm install --save x is not reconstructed as separate argv entries.
• The fallback get_hermes_home edits in plugins/disk-cleanup/disk_cleanup.py and plugins/hermes-achievements/dashboard/plugin_api.py recurse when the constants import fails.

Suggested changes

• Separate parser, shell=False argv, and intentional-shell command-string use cases; preserve a real argv for the first two rather than returning a raw one-item list.
• Add regression tests for Windows tokenization, migrated shell hooks/ACP args, disk cleanup, Node arguments, and fallback imports.

This is an automated hermes-sweeper review.

[teknium1]

safe_split_command is defined in this PR with only a command parameter, so this existing posix=True call becomes a TypeError. Either preserve the needed keyword contract or remove/rework this call with a tokenizer appropriate for this parser.