Collapse shell policy phase machinery

[Aaronontheweb]

Summary

• replace the internal stage-result hierarchy, terminal-state machine, and separate stage-owner classes with one direct coordinator method
• preserve the same ten authorization phases, ordering, cancellation checks, actor-evidence boundary, coverage, and trace semantics
• replace 1,664 lines of production-impossible stage tests with focused path-fact and atomic-state regressions plus an end-to-end actor-cancellation regression
• remove 254 production lines and 16 control-flow lines; cumulative policy control-flow is now below the frozen baseline

Verification

• Netclaw.Security.Tests: 946 passed
• Netclaw.Actors.Tests: 3,396 passed; one expected Windows-only skip
• coordinator/fixture/disposition replay: 420 passed
• security evidence contract: 26 passed
• channel/recovery/headless/subagent focus: 279 passed
• strict validation passes for both active shell-policy OpenSpec changes
• headers, changed-file formatting, diff check, and changed-file Slopwatch pass