Update identifier test to reflect first-character restriction
Add tests for "a OP b" operator expressions
Fix ordering issue with operator matching
Checkpoint expression matches
Add notes about checkpointing in META-SEXP
Add tests for widget phrases
Split widget phrase into multiple rules
Add widget AST struct
Add phrases code to system
Add wait-for statement tests
Add statement struct
Add initial wait-for statement code
Add package decl for phrases
Move join-list to utils file, swap delimiter/list args, add dict constructor
Fix ordering issue
At notes about statements
Add at-phrase code
Add view-statement code
Add view statement tests
Add validate statement tests