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/18-tilde-expansion.md

@@ -0,0 +1,27 @@
+# 18 — Path expansion (`~`, `*`, `**`)
+
+**Status:** open
+**Related:** #13 shell globbing
+
+Path expansion for `~` is not available. Commands like:
+
+```
+!cat ~/Notes/jobs_board.md
+```
+
+fail with:
+
+```
+cat: ~/Notes/jobs_board.md: No such file or directory
+```
+
+The `~` and other expansions are passed literally to the command rather than being expanded to `$HOME`.
+
+## Requirements
+
+- `~` at the start of a word should expand to `$HOME`
+- Should work in both backtick and `!` prefix contexts
+
+### To invesitigate/decide
+
+- How should it interact with quoting (quoted `~` should not expand), should single/double quotes be used? both? or something else?