Fix crash when a switch case's last statement is formatter-ignored

[nenadvulic]

Summary

Fixes #309.

Linting or formatting a file with // swift-format-ignore on the last statement of a switch case crashes:

switch val {
case .foo:
  // swift-format-ignore
  print("Foo")
case .bar:
  print("Bar")
}

SwiftFormat/PrettyPrint.swift: Assertion failed: Too many unresolved delimiter token lengths.

Root cause

visit(SwitchCaseSyntax) emits an .open group after the case label and attaches the matching .close as an after token on the case's last token. When the last statement is formatter-ignored it is emitted verbatim and its tokens are never visited (the node is skipped), so the after close tokens are dropped and the group is never closed.

This is the same hazard that visit(CodeBlockItemListSyntax) already documents and avoids ("the tokens after item.lastToken would be ignored and leave unclosed open tokens").

Fix

When the case's last statement is formatter-ignored, attach the closing tokens before the next token (the next case or the closing brace) instead of after the case's last token — mirroring the existing handling for empty cases.

Tests

Added testIgnoreStatementInSwitchCase and testIgnoreLastStatementInSwitchCase to IgnoreNodeTests. Both crash without the fix and pass with it. Full test suite passes (934 tests, 0 failures).