fix: track bare drive switches (d:) for cwd memory

PowerShell/cmd users hop drives with a bare 'd:' — no cd keyword — so the
typed-command tracker never saw it, the pane's cwd stayed at its creation
directory, and the session snapshot restored it to home. Treat a bare
drive-letter line as a cd to the drive root; the main-process existence
check drops it on platforms without drive letters.

src/renderer/src/terminal/cwdTracker.ts

@@ -4,8 +4,9 @@
  * Two signals feed the same store:
  *   1. the shell itself, over OSC 7 (`file://host/path`) or ConEmu's OSC 9;9 —
  *      exact, but only present when shell integration is on;
- *   2. the command the user typed, matched against the `cd` family — the
+ *   2. the command the user typed, matched against the `cd` family plus the
- *      fallback that works with no shell cooperation at all.
+ *      bare drive switch (`d:`) of cmd.exe / PowerShell — the fallback that
+ *      works with no shell cooperation at all.
  *
  * Both are platform-neutral: path resolution and existence checks happen in the
  * main process (`src/main/cwd.ts`) where node's `path` lives, so nothing here
@@ -21,14 +22,26 @@
  */
 const CD_COMMAND = /^\s*(?:cd|chdir|sl|set-location|pushd|push-location)(?:\s+([\s\S]*))?$/i
 
+/**
+ * Bare drive switch (`d:`, `D:`) — cmd.exe and PowerShell change the current
+ * drive with no `cd` keyword at all, and it is the common way to land on
+ * another drive on Windows. Treated as a cd to the drive root; the main
+ * process's existence check quietly drops it on platforms where drive
+ * letters mean nothing (POSIX resolves it to a nonexistent relative path).
+ */
+const DRIVE_SWITCH = /^\s*([a-zA-Z]):\s*$/
+
 /**
  * Return the argument of a cd-style command line, or null when the line is not
- * one. An empty string means "bare cd" (the shell's home directory).
+ * one. An empty string means "bare cd" (the shell's home directory). A bare
+ * drive switch yields the drive root (`D:\`).
  */
 export function cdArgument(line: string): string | null {
   const match = line.match(CD_COMMAND)
-  if (!match) return null
+  if (match) return (match[1] ?? '').trim()
-  return (match[1] ?? '').trim()
+  const drive = line.match(DRIVE_SWITCH)
+  if (drive) return `${drive[1].toUpperCase()}:\\`
+  return null
 }
 
 /** Payload of an OSC 9 sequence that follows the ConEmu `9;<path>` convention. */