[BUG] Claude Desktop CC mode: Windows drive-letter backslash stripped from project paths

Description

Claude Desktop's CC/super mode cannot connect to any local project on Windows. Every project in the picker shows path not found: E:claude_GL (and similar for all other projects). The backslash after the drive letter is missing — E:\claude_GL becomes E:claude_GL.

Evidence that the real path is known (not a key-decoding issue)

The error displays E:claude_GL with the underscore intact. The .claude/projects/ directory key for this project is E--claude-GL (hyphen, not underscore). If the app were decoding the key, it couldn't recover the underscore. Instead, the app clearly has the real path string E:\claude_GL from a clean source (session JSONL cwd or similar), and the backslash gets eaten downstream.

This matches a double-unescape pattern: JSON "E:\\claude_GL" parsed correctly on first pass, then unescaped a second time where \c collapses to c (JS string escape), producing E:claude_GL.

To reproduce

1. Windows 11, any project on a drive with underscores in the path (e.g. E:\claude_GL, E:\claude_all4one)
2. Open Claude Desktop > CC/super mode > project picker
3. Every project shows "path not found" with the backslash after the drive letter stripped

Expected behavior

Projects resolve to their correct paths (e.g. E:\claude_GL) and connect normally.

Environment

• OS: Windows 11 Pro 10.0.26200
• Claude Desktop: v1.11847.5 (Microsoft Store)
• Claude Code CLI: v2.1.170
• All projects affected (not just one)

Additional context

• claude_desktop_config.json has correct paths with proper escaping (E:\\claude_GL)
• Real directories exist on disk (Test-Path confirms)
• CLI sessions work fine, only the Desktop app CC mode project picker is broken
• The .claude/projects/ directory keys use lossy encoding (_ to -), but this bug is NOT a key-decoding issue. The underscore being intact in the error proves the app has the real path and mangles it during string processing

Related issues (same backslash-swallowing family on Windows)

• #19108: VS Code extension corrupted project path handling, backslashes mangled in projects transformation
• #18996: EDITOR env var causes backslash before .claude to be stripped (goran\.claude becomes goranclaude)
• #53340: Claude Desktop fails to surface project-level folders despite intact data on disk