fix: sanitize control characters in paths printed on quit

[carfeii]

Fixes #615.

gdu's TUI is built on tview, which already strips control characters from the paths it renders on screen. But two features print a path directly to the terminal after the TUI has already stopped, bypassing that protection: quitting with Q prints the current directory's path, and quitting after marking files prints each marked path. A scanned directory or file's name has no character restrictions, so a crafted name can inject terminal escape sequences into either printed line.

Adds sanitizePathForDisplay (tui/tui.go), replacing control characters with the Unicode replacement character, applied at both doQuit's currentDirPath print (tui/keys.go) and printMarkedPaths (tui/tui.go).

Verified against a directory containing a subdirectory named with a raw OSC title-set escape sequence, navigating into it and quitting with Q, output redirected to a file and inspected as a hex dump. Confirmed no regression with a normal directory path. tui package tests pass.

One honest caveat: I fixed printMarkedPaths using the identical pattern as the confirmed Q-path sink (same unsanitized fmt.Fprintf shape, same sanitizer), but I wasn't able to independently reproduce that specific call site live within the time I had. Marking an entry worked (confirmed via the checkmark in the UI itself), but the raw output capture never showed the expected printed line on quit despite a few timing adjustments on my end. The fix should still be correct by inspection, just flagging that I'm not claiming it as independently reproduced the way the Q path is.

[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.86%. Comparing base (fe605ec) to head (f1d803d).

Files with missing lines	Patch %	Lines
tui/tui.go	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #616      +/-   ##
==========================================
- Coverage   85.89%   85.86%   -0.03%     
==========================================
  Files          55       55              
  Lines        6329     6334       +5     
==========================================
+ Hits         5436     5439       +3     
- Misses        689      690       +1     
- Partials      204      205       +1     

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[dundee]

Thanks!