Add issues #16–#23

#16 multiline shell commands
#17 _ scope (global vs local)
#18 path expansion (~)
#19 nested commands trigger prompt2
#20 simplify backtick return value
#21 prompt redesign
#22 implicit interactive commands (drop ! prefix)
#23 general cleanup and refactor

issues/22-implicit-interactive-commands.md

@@ -0,0 +1,21 @@
+# 22 — Implicit interactive commands (drop `!` prefix)
+
+**Status:** open
+
+In the REPL, maybe we can get away with not needing the `!` prefix.
+
+Lua already attempts to run input as a statement. If that fails, it assumes it might be an expression (e.g. `1 + 2`) and wraps it in `return(...)`. If *that* also fails, we could try wrapping it with `!` prefix semantics as a third fallback.
+
+## Execution order
+
+1. Try as Lua statement
+2. Try as Lua expression (`return ...`)
+3. Try as shell command (interactive execution)
+
+## Considerations
+
+- Ambiguity: `ls` is not valid Lua, so it would fall through to shell — this is the desired behaviour
+- But `print` is valid Lua (it's a value) — so `print` alone wouldn't trigger shell
+- What about `git status`? Not valid Lua, would correctly fall through to shell
+- Error messages: if all three fail, which error do we show?
+- Performance: three parse attempts per input line