v0.8.6

• Supershells: Preserve stderr as subshells do
  Supershells in Bash++ now handle stderr identically to subshell
  substitution, matching Bash 5.3's native supershells.
  Previously, supershells in 5.2-compatibility mode discarded stderr; now it
  is preserved.
  Added regression test for supershell stderr handling.
• Dynamic cast codegen: Don't force-quote reference code
  Fixed edge-case bug where generated code for dynamic casts would
  incorrectly add quotes around the reference code. Now preserves original
  quoting as written in source.
  Added regression test for dynamic cast quoting.
• Parser: Never override lexer's positive lvalue judgment
  Fixed bug where parser could incorrectly override the lexer's
  determination that a token could be an lvalue.
  Ensures correct handling of lvalue/rvalue distinctions, especially around
  redirections and pipes.
  Added regression test for this behavior.
• Test suite: Run tests for Bash 5.2 and 5.3
  Tests are now run twice if Bash >=5.3 is installed:
  once for 5.2 compatibility, once for 5.3.