Add project issues for lush (Lua + shell) features

Defines syntax decisions and implementation plan across 7 issues:
- backtick command execution returning {code, stdout, stderr}
- ${expr} interpolation in backticks
- $SIGIL env var read/write
- argv parsing, piping, and redirection (future)

issues/04-argv-parsing.md

@@ -0,0 +1,26 @@
+# 04 — Implement argv parsing (tokenize command strings)
+
+**Status:** open
+**Blocked by:** #01
+**Blocks:** #06
+
+Since we're not using a shell, we need our own command-line tokenizer to split a command string into `argv[]`.
+
+## Must handle
+
+- Simple whitespace splitting: `ls -l /tmp` → `["ls", "-l", "/tmp"]`
+- Single-quoted strings: `echo 'hello world'` → `["echo", "hello world"]`
+- Double-quoted strings with escapes: `echo "hello \"world\""`
+- Backslash escaping outside quotes: `echo hello\ world`
+- Mixed quoting: `echo "it's a test"`
+
+## May handle (depending on #01 decisions)
+
+- Variable/expression interpolation: `echo $HOME` or `echo ${dir}`
+- Glob expansion: `ls *.lua` (could also defer to a later issue)
+
+## Implementation
+
+- Standalone C module, likely `lcmd_parse.c` or part of `lcmd.c`
+- Returns a `char **argv` (NULL-terminated) + argc count
+- Must handle memory allocation/cleanup