Redesign issue #10: bare-word commands now work in both scripts and
the REPL via a parser-level heuristic (identifier + non-exception-list
token → shell command). Add runtime fallback for string-arg syntax
(echo "hello"), double-dash flag handling, and classification examples.
Add issue #12 for path-based command execution (./script, /bin/ls, ~/bin/deploy).
Add testes/lush/commands-interactive.lua as a design playground covering
result table structure, exit codes, commands inside Lua blocks, _ behaviour,
runtime fallback, Lua variable shadowing, and interleaved Lua/shell.
Rewrite #10 with refined interactive command design: bare-word REPL
fallback instead of ! prefix, result table assigned to _, same shape
as captured commands. Add #11 for Ctrl-C clearing the current line
instead of exiting the REPL.
Mark issues #02 (backtick lexing/parsing), #03 (command execution
runtime), and #04 (argv parsing) as resolved. Add new issues for
configuration (#08), programmable prompt (#09), and interactive
command execution (#10).
