ShellSyntaxTree 0.3.0-alpha.3

This prerelease adds the PowerShell state and value proofs needed for the
Netclaw approval-policy integration. It does not change the public v0.3 API
surface, and the conservative v0.2 projection remains available.

Added

• Apply the explicit PowerShell initial-state contract to command identity,
  native-versus-cmdlet argument binding, working-directory attribution,
  redirects, automatic HOME, and USERPROFILE values.
• Preserve argument-binding provenance through static current-scope
  Invoke-Expression payloads while keeping decoded child-host state isolated.
• Expand the generated PowerShell corpus from 422 to 491 entries with direct,
  wrapper, alias, script, redirect, child-host, and unknown-state cases.

Security and compatibility

• Treat aliases as capable of shadowing built-ins and path-shaped command
  names; exact argument binding requires constrained, unmutated command
  resolution.
• Invalidate following authorization state after uninspected scripts and
  unproved in-process invocations instead of retaining stale exact values.
• Keep supported non-pipeline bodies of unknown receivers visible and
  incomplete, while failing an unproved interior pipeline atomically with
  empty authorization projections.
• Preserve ordinary v0.2 compatibility leaves under ambient uncertainty and
  keep the public v0.3 API snapshot unchanged.