fix: correct Windows path encoding/resolution in cvfs

[hen-corix]

Summary

• get_home(): prefer USERPROFILE over HOME on Win32 — Git Bash sets HOME to an MSYS2 virtual path (e.g. /c/Users/foo) that native Win32 file APIs can't resolve
• msys2_to_win(): convert Git Bash MSYS2 drive-mount paths (/d/workspace/foo) to proper Windows paths (D:/workspace/foo) before processing
• resolve_path(): handle Windows absolute paths (C:/...) correctly; normalize Unix.realpath output which may return backslashes on Win32
• project_path(): match Claude Code's actual encoding — replace any character outside [a-zA-Z0-9-] with - (previously only /, \, : were replaced, missing underscores, spaces, and other chars)
• get_cwd_from_jsonl() / get_project_path_from_dir(): read the real cwd from JSONL conversation files instead of trying to reverse-decode the encoded directory name (which is lossy — hyphens in folder names are indistinguishable from encoded path separators)
• Replace all Sys.getenv "HOME" with get_home() throughout

Context

These fixes address three bugs on Windows:

1. claude-mv always reported "Error: No conversation found"
2. claude-ls reported "No conversations found in ."
3. claude-ls / claude-clean failed for project paths containing hyphens, uppercase letters, underscores, or spaces

Test plan

• claude-ls in a Windows project directory returns conversations
• claude-ls in a path with underscores (e.g. D:\workspace\My_Project) finds the correct Claude project directory
• claude-ls with a Git Bash MSYS2 path argument (e.g. /d/workspace/foo) resolves correctly
• claude-clean shows correct project paths (not mangled by lossy hyphen substitution)
• claude-mv successfully finds and moves conversations on Windows
• All existing behaviour unchanged on Linux/macOS

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