fix(windows): quote diff-pane argv so git receives the delta pager intact

The previous Windows diff fix moved delta into git's pager
(`-c core.pager=delta --paging=always`), but alacritty_terminal joins
PTY argv into a single CreateProcess command line and only quotes
arguments when `Options::escape_args` is set — and we left it at the
default `false`. The pager spec split on its space, git rejected
`--paging=always` as an unknown global option and exited immediately,
and the reaper closed the pane before the error could render: the diff
"opened" and vanished showing nothing. Any file path containing a space
would split the same way.

Enable `escape_args` for diff panes, whose argv is built in code.
Config-shell args stay raw to match upstream alacritty's handling of
user-authored shell arguments.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: mathix420

alacritree/src/session.rs

@@ -306,9 +306,14 @@ impl Session {
             working_directory: working_directory.clone(),
             drain_on_exit: false,
             env: config.env.clone(),
-            // `Options` has a Windows-only `escape_args` field; leaning on
-            // `Default` keeps the literal compilable on every target.
-            ..Default::default()
+            // Windows has no argv: alacritty_terminal joins these args into a
+            // single CreateProcess command line, quoting them only when this
+            // is set.  Diff panes pass argv built in code, where an arg with a
+            // space (delta's pager spec, file paths) must survive as one
+            // argument; shell args from alacritty.toml stay raw to match
+            // upstream alacritty.
+            #[cfg(windows)]
+            escape_args: matches!(kind, SessionKind::Diff { .. }),
         };
 
         // alacritty routes OSC 7 / signals by this id, so each session needs its own.