Fix packaged worker native broker read starvation

[dovvnloading]

Summary

• Fix the packaged worker transform timeout by polling PeekNamedPipe with a bounded 5 ms wait before synchronous ReadFile calls.
• Add a regression test proving the pipe waits for available bytes before reading.
• Update ADR-0001 Phase 2 evidence and the qualification runbook with the verified result and remaining release gates.

Root cause

The worker starts a broker reader thread so cancellation frames remain live while Pillow transforms. A blocking synchronous native read could starve the packaged transform thread under the AppContainer, so the request stopped at input_complete even though the provider and transport contracts were otherwise valid. Availability polling keeps the reader responsive without changing framing, authentication, direction, or sequence validation; pipe errors still fail closed.

Validation

• python -m pytest -q — 260 passed, 1 skipped.
• python -m pytest tests/test_phase2_native_broker.py -q — 10 passed, 1 skipped.
• python -m compileall -q backend\\cortex_backend\\execution tests.
• git diff --check.
• Fresh packaging/build_recipe_worker.ps1 build.
• Strict signed AppContainer/broker qualification passed: prepare, input_chunk, input_complete, and collect_output; bounded cleanup left no worker process.
• Temporary diagnostic probes were removed.

Release-gate status

This closes the packaged provider-transform qualification blocker. Phase 2 remains blocked on dedicated signed-worker watchdog/cancellation and hostile-decoder corpus evidence, external security review, and production lifecycle wiring. No production provider launch is enabled by this PR.