Add hidden root execution backend

WH
25d ago
+16536-214

Summary

Adds the hidden root transport, execution, and recovery implementation for redesign slices 04ā€“06. The backend validates its libsu transport, records durable execution evidence, and only signals or settles executions after exact ownership checks. Production wiring still selects AppUidBackend, so this PR does not enable Superuser Mode or change Normal Mode behavior.

Included tracker

Includes the Superuser Runtime Redesign specification and implementation-ticket tracker from merged PR #5.

Validation

  • Root implementation validation: make test passed (318 tests across 29 suites).
  • Focused root runtime tests passed (222 tests across 14 suites); lint and git diff --check were clean.
  • Physical-device qualification with real libsu: NOT RUN.

Stack

Base: PR #3, codex/close-recovery-to-launch-ownership-race
Head: codex/rootbackend-transport-execution-and-recovery at the merged tracker commit 5c9f78c6.
Managed State is stacked as PR #6 on this branch. The later folder/script/tuning slice remains separate.