ShellSyntaxTree 0.3.0-alpha.2

This prerelease completes the stable-v0.3 boundary between PowerShell script
blocks proved to be data and blocks that may execute. It does not change the
public v0.3 API surface, and the conservative v0.2 projection remains
available.

Added

• Keep script blocks passed to a proved Write-Output receiver opaque under a
  constrained PowerShell baseline instead of inventing nested command
  occurrences.
• Preserve unknown script-block receivers as visible, incomplete execution
  regions, and expose proved local Invoke-Command bodies as synchronous
  command occurrences.

Security and compatibility

• Require bounded command-resolution proof before classifying a script block as
  data. Default runspace state remains conservative.
• Track exact command mutations through authored and canonical alias identities.
  This prevents exact module-qualified-looking aliases and echo alias chains
  from hiding an executable script block.
• Preserve unrelated-name precision and reset runspace-local mutations at fresh
  parallel child-runspace boundaries without clearing process-wide uncertainty.
• Expand the generated PowerShell corpus to 422 entries, all validated against
  the live PowerShell parser and the PII audit.