format on semicolon (onTypeFormatting)

[michaeldistel]

Summary

Implement textDocument/onTypeFormatting to auto-format the current line when the user types ; or END_*.

Scope

• Trigger characters: ;, _ (catches END_IF, END_FOR, etc.)
• Formats indentation of the current line only
• Respects user formatting options (tab size, insert spaces)
• Registered in LSP server capabilities

Implementation Notes

• Add onTypeFormattingProvider to LSP capabilities in server.ts
• Reuse indentation logic from FormattingProvider

Acceptance

• Typing ; corrects indentation of current statement
• Typing END_IF / END_FOR / END_WHILE normalizes indent
• No formatting when triggered in comments or strings
• Tests pass