extras/powershell_greeting: fix WezTerm logo stretch (iterm + preserveAspectRatio)

kitty-direct sends c= but no rows through ConPTY (the terminal guesses the height and stretches); the plain kitty type needs tty pixel queries that ConPTY drops. The iterm type with preserveAspectRatio=1 letterboxes any aspect ratio.

extras/powershell_greeting/README.md

@@ -16,7 +16,7 @@ terminals.
 | JSON parsing | `jq` / `python3` / grep | `ConvertFrom-Json` (built-in) |
 | MIME detection | `file --mime-type` | PNG/JPEG/GIF magic bytes |
 | GIFs | `gifsicle` + `kitten icat` | none: static first frame in Windows Terminal, animated in WezTerm (its `kitty-direct` plays the GIF) |
-| fastfetch logo | `--logo-type kitty --logo ... --logo-width 35` | `sixel` in Windows Terminal, `kitty-direct` in WezTerm, no image elsewhere |
+| fastfetch logo | `--logo-type kitty --logo ... --logo-width 35` | `sixel` in Windows Terminal, `iterm` (aspect-preserving box) in WezTerm, no image elsewhere |
 | Logs | `~/.config/j621Logos/logs.log` | `%APPDATA%\j621Logos\logs.log` |
 
 ## Install
@@ -99,8 +99,10 @@ switch, or just edit the file.
 - **No image logo in Windows Terminal**: WT 1.22+ is required for sixel;
   update with `winget upgrade Microsoft.WindowsTerminal`.
 - **WezTerm**: kitty graphics must be on - `config.enable_kitty_graphics = true`
-  in `~/.wezterm.lua`. If the default looks wrong, try
-  `J621_LOGO_TYPE=kitty`, `sixel`, or `iterm`.
+  in `~/.wezterm.lua`. The default uses the `iterm` logo type with
+  `preserveAspectRatio`, which never stretches. If something looks off, try
+  `J621_LOGO_TYPE=kitty-direct`, `kitty`, or `sixel` (note: through ConPTY,
+  plain `kitty` falls back to ASCII and `kitty-direct` stretches tall images).
 - **VS Code / other terminals**: no image protocol, so the greeting prints a
   plain fastfetch on purpose (no fetch delay). `J621_ALWAYS_FETCH=1` still
   fetches and prints the link.