[phatloi0010]

Fixes #3159

Summary

Enforces newline sensitivity (self.same_line_as_prev()) across the four remaining statement and postfix continuation sites in compiler/crates/hy-syntax/src/parser.rs:

1. Tok::Kw("return") (Parser::parse_stmt, lines 914–929):
   • Stop parsing return value expressions when !self.same_line_as_prev(), preventing a bare return from consuming the next line's statement or subsequent unbraced match / select arm head (none => return, <-quit:\n return), and preserving values.is_empty() so Checker::process_return (loans.rs:8950) enforces HYB-E3104 on named borrow results.
2. Tok::Kw("break") and Tok::Kw("continue") (Parser::parse_stmt, lines 997–1030):
   • Require self.same_line_as_prev() && !matches!(self.nth(1), Tok::Punct("{")) before consuming loop as a break loop / continue loop label, preventing a plain break or continue from stealing the loop keyword of a loop { ... } statement on the next line.
3. Parser::parse_postfix ({ composite literal attachment & [ index/slice/type-arg postfix, lines 2177–2248):
   • Require self.same_line_as_prev() before attaching { as a struct composite literal T{...} or [ as an index/slice/type-argument postfix, preventing y := xs followed by [0] or { ... } on the next line from fusing into y := xs[0] or xs{...}.

Tests

• compiler/crates/hy-syntax/src/parser.rs:
  • bare_return_does_not_consume_next_line_or_arm_head
  • break_and_continue_do_not_consume_next_line_loop_stmt
  • line_leading_bracket_and_brace_do_not_fold_into_previous_expr
• compiler/crates/hy-check/src/loans.rs:
  • newline_after_bare_return_and_slice_alias_enforces_tier0_checks (verifies HYB-E3104 on bare return of named pointer borrow before a next-line expression, and HYB-E3006 when mutating a const slice alias y := xs followed by [0] on the next line).

---

Note: Re-queued from #3160 onto latest main (a1490f03, behind_by: 0) because #3160 fell past the 100-item open PR page cap (#3852+). #3160 is closed in favor of this PR.