e[Bug] Session history not displayed in UI panel when VS Code workspace opened at drive root path

Title: VS Code extension: session history is empty when workspace is opened at a drive root

Body:

Description
When the VS Code workspace folder is opened directly at a drive root (e.g. P:\, a mapped network drive), the graphical Claude Code panel never shows any session history — neither auto-resuming the last session on open, nor listing past sessions via the history (clock) button.

Environment

Extension version: 2.1.216
OS: Windows
Workspace path: P:\ (mapped network drive root, no subfolder)

Steps to reproduce

Map a network drive to a letter (e.g. P:)
Open that drive root directly as a VS Code workspace folder (File > Open Folder... > P:\)
Use Claude Code in the graphical panel across a few sessions
Reload the window / reopen the panel
Click the session history (clock) icon

Expected behavior
Previous sessions for this project appear in the history list, and/or the last session auto-resumes on open — as it does for projects opened in a regular subfolder.

Actual behavior
The history list is always empty ("No conversations found in this project" is not shown here — the list is just blank with no message). A new blank "Untitled" conversation opens every time.

Additional context

~/.claude.json does contain a valid project entry for this path ("P:/") with populated usage stats (lastCost, lastStartTime, etc.), confirming the sessions were recorded.
Extension debug log shows launch_claude is invoked with "cwd":"p:\\" (lowercase, backslash) each time.
Switching to terminal mode (claudeCode.useTerminal: true) and running /resume followed by Ctrl+A (show all projects) correctly lists all past sessions for p:\, and resuming from there works fine.
Running the standalone CLI (claude --resume, same version 2.1.216) in the integrated terminal also correctly lists and resumes sessions for this project.
CLAUDE_CONFIG_DIR is not set in either context.

This suggests the graphical panel's session-list/auto-resume path handles drive-root project paths differently (and incorrectly) compared to the terminal-mode /resume picker and the standalone CLI, which both work correctly for the same path.

Workaround
Enable claudeCode.useTerminal and use /resume + Ctrl+A to see and resume sessions.