fixes #287161

The bug was caused by double-navigation when typing ../:

• Extension side: resolveCwdFromCurrentCommandString() was pre-resolving ../ paths, setting cwd to the parent directory
• Completion service side: When processing ../, it did URI.joinPath(cwd, '../') which navigated up AGAIN from the already-resolved parent

So typing ../ from vscode resulted in:

• Extension resolved cwd to Repos (parent)
• Completion service then did joinPath(parent, '../') = meganrogge(grandparent)
• Children shown were from grandparent, showing Repos instead of xterm.js

Added a check in resolveCwdFromCurrentCommandString to skip pre-resolution for paths containing .. to fix this.