test(agent): add agents api module boundary smokes

[chubes4]

Summary

• Splits the existing Agents API bootstrap smoke into focused module-level coverage for bootstrap, registration semantics, and product-namespace isolation.
• Adds a shared pure-PHP smoke harness so the in-repo agents-api/ module can be exercised without loading Data Machine product runtime.
• Adds a static no-product-imports smoke that fails if agents-api/ imports Data Machine product namespaces for steps, jobs, admin, handlers, retention, flows, pipelines, queues, or content ops.

Tests

• php tests/agents-api-bootstrap-smoke.php && php tests/agents-api-registration-smoke.php && php tests/agents-api-no-product-imports-smoke.php
• php -l tests/agents-api-smoke-helpers.php && php -l tests/agents-api-bootstrap-smoke.php && php -l tests/agents-api-registration-smoke.php && php -l tests/agents-api-no-product-imports-smoke.php
• git diff --check origin/main...HEAD
• homeboy lint data-machine --path /Users/chubes/Developer/data-machine@agents-api-module-smokes --changed-since origin/main
• homeboy audit data-machine --path /Users/chubes/Developer/data-machine@agents-api-module-smokes --changed-since origin/main

Closes #1639

Closes #1639.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Drafted the smoke-test split, ran focused verification, and prepared the PR. Chris remains responsible for review and merge.

[homeboy-ci]

Homeboy Results — data-machine

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Test

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Audit

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Tooling versions

• Homeboy CLI: homeboy 0.124.11+99191a6b
• Extension: wordpress from https://github.com/Extra-Chill/homeboy-extensions
• Extension revision: 36ceece
• Action: Extra-Chill/homeboy-action@v2