Materialize PCP deployability follow-ups

[promachina]

Summary

• Materialize the public PCP copy from the verified pcp-internal deployability follow-up tree.
• Includes the public-safe STATE_DIR, token-file, probe-port, and worker-concurrency runtime changes.
• Keeps private extension paths removed through the public cut overlay.

Verification

• docs/verify-public-cut.sh /tmp/pcp-public-cut-k8s-followups from pcp-internal
• Public materialized tree: 303 tests passed, 2 skipped

Refs deltawave-tech/pcp-internal#14
Refs deltawave-tech/pcp-internal#15