ShellSyntaxTree 0.3.0-alpha.4

This prerelease corrects PowerShell occurrence completeness to describe the
authored command text instead of ambient command resolution. It does not
change the public v0.3 API surface, and the conservative v0.2 projection
remains available.

Changed

• Keep static authored PowerShell commands, pipeline stages, decoded child
  commands, and proved script-block receivers complete under the default
  initial-state mode.
• Use an explicit native or .ps1 path spelling to select authored argument
  binding without inspecting the executable, PATH, profiles, modules,
  aliases, functions, inherited variables, or prior runspace state.
• Keep unqualified .ps1 binding, dynamic command identities, computed
  execution, unknown receivers, and unsupported executable syntax strict.

Security and compatibility

• Preserve Unknown effective loop values when the submitted source does not
  prove the runtime binding value.
• Invalidate later command proofs after a matching mutation that is visible in
  the submitted source.
• Keep provider-sensitive repeated loops incomplete when an unknown path could
  mutate command resolution before a later visit.
• Preserve all public signatures, the v0.2 compatibility projection, and the
  491-case generated PowerShell corpus.