feat: expose safe pipeline configuration contracts

[chubes4]

Summary

• add owner-safe abilities to resolve pipelines by ID or exact stable name and return normalized pipeline/flow step configuration
• add opaque SHA-256 revisions and byte-exact compare-and-swap writes for supported pipeline and flow step fields
• preserve flow pre-save validation, handler schema/default processing, audit hooks, and explicit unavailable/not-found/conflict errors
• cover lookup, valid pipeline/flow updates, unknown fields, stale writes, missing objects, and authorization

Validation

• homeboy review lint --placement local --changed-only --summary (PHPCS and PHPStan level 7 passed)
• homeboy review audit --placement local --profile architecture --changed-since origin/main --summary
• php tests/prefix-policy-audit.php
• php tests/flow-config-pre-save-filter-smoke.php
• PHP syntax and git diff --check

Test Infrastructure

The focused/full Homeboy test runner could not start because the local cached WP Codebox CLI bundle is missing (packages/cli/dist/index.js), and no Lab runner was available. A direct isolated WordPress PHPUnit bootstrap was also blocked by unavailable local test-database credentials. No production database or configuration was used or modified; GitHub CI remains the integration-test authority for this PR.

Closes #3056