feat(shell): add bash-style history expansions and interactive keybindings

- Replicate bash bang-operations (!^, !*, !string, etc.) via abbreviations
- Add Ctrl+G for previous path head insertion
- Add Ctrl+F for interactive history substitution
- Add Ctrl+Alt+U to quickly replace command tokens
- Update README documentation for all new features

functions/expand_bang_string.fish

@@ -0,0 +1,23 @@
+function expand_bang_string
+    # Fish 4.x passes the matched token as argv[1]
+    set -l token $argv[1]
+    if test -z "$token"
+        set token (commandline -t)
+    end
+    
+    # Remove the '!' to get the search query
+    set -l query (string sub -s 2 -- $token)
+    
+    if test -n "$query"
+        # Search history for a prefix match
+        set -l match (builtin history search --prefix --max=1 -- $query)
+        
+        if test -n "$match"
+            echo -- $match
+            return
+        end
+    end
+    
+    # If no match or empty query, return the token so it doesn't vanish
+        echo -- $token
+end