fix(hir): preserve unsupported lowering states

[hongjr03]

Summary

• distinguish parser recovery, invalid syntax, and unsupported HIR lowering states
• retain source mappings and syntax kinds for unsupported expressions and statements
• lower streaming with ranges plus clocking events, modifiers, and default references
• update downstream statement consumers and add regression coverage

Verification

• cargo test -p hir (96 passed)
• cargo test -p ide document_symbols (1 passed)
• cargo check --workspace --all-targets
• cargo test -p hir valid_unlowered_expression_is_not_parser_missing