feat: support definition-only agents

[chubes4]

Summary

• allow registered agent definitions to opt out of Data Machine's automatic default reconciliation through meta.datamachine_default_materialization=false
• report opted-out definitions separately as definition_only without creating rows, access grants, directories, scaffolds, or reconciliation hooks
• preserve explicit, idempotent exact-scope materialization and all existing default reconciliation behavior

Closes #3034

Existing Primitive Investigation

Agents API already separates declarative registration from host-owned materialization. WP_Agent preserves generic meta, wp_materialize_agent_identity() validates the registered definition and constructs an exact WP_Agent_Identity_Scope, and WP_Agent_Identity_Store::materialize() owns idempotent persistence. It does not expose a default-materialization policy field or filter; its registration docs explicitly leave that decision to hosts.

This PR therefore does not change the generic Agents API dependency or add a parallel materialization path. It adds only a Data Machine consumer-owned reconciliation policy in existing definition metadata.

Contract

Definitions retain today's behavior by default. Only an explicit strict-false marker opts out:

'meta' => array(
    'datamachine_default_materialization' => false,
),

Normal AgentRegistry::reconcile() reports that slug under definition_only before resolving a default owner or invoking the identity store. Explicit wp_materialize_agent_identity() calls continue through the registered Agents API definition and Data Machine identity store with the requested owner and instance key, including duplicate-key concurrency handling.

Runtime bundle/import reconciliation remains default-on for definitions without the marker and continues skipping marked definition-only defaults.

Compatibility

• existing definitions and the default system agent remain default-materialized
• existing created, existing, and skipped outcomes retain their meaning
• reconciliation summaries add the definition_only outcome
• no owner_resolver=0, post-reconciliation deletion, product-specific behavior, or generic-layer vendor vocabulary is introduced

Tests

• php tests/agent-registry-materializer-smoke.php passes all 37 assertions
• php tests/runtime-agent-bundle-reconcile-smoke.php passes
• php tests/agent-prune-resurrection-smoke.php passes
• homeboy review lint data-machine --path . --placement local --changed-only --summary passes
• homeboy review audit data-machine --path . --placement local --profile pr --changed-since origin/main --json-summary passes with no introduced findings
• configured Homeboy test selection identifies 129 tests but returns an unstructured zero-test failure; the focused direct tests above pass, and the runner defect is tracked in fix: WordPress test gate reports zero tests for explicit Roadie test homeboy#10601

[homeboy-ci]

Homeboy Results — data-machine

Lint

✅ review lint — passed

ℹ️ Full options: homeboy self docs commands/lint
Deep dive: homeboy review lint data-machine --changed-since 2cb96b7

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-review-lint-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-review-lint-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/30370601930

Test

❌ review test — timed out

ℹ️ The test runner failed before producing structured results. See raw_output.stderr_tail / raw_output.stdout_tail for the underlying error (bootstrap failure, missing deps, DB connection, etc.).
ℹ️ To run specific tests: homeboy review test data-machine -- --filter=TestName
ℹ️ Auto-fix lint issues: homeboy refactor data-machine --from lint --write
ℹ️ Collect coverage: homeboy review test data-machine --coverage
ℹ️ Analyze failures: homeboy review test data-machine --analyze
ℹ️ Pass args to test runner: homeboy review test -- [args]
ℹ️ Full options: homeboy self docs commands/test
Deep dive: homeboy review test data-machine --changed-since 2cb96b7

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-review-test-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-review-test-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/30370601930

Audit

❌ review audit — failed

Deep dive: homeboy review audit data-machine --changed-since 2cb96b7

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-review-audit-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-review-audit-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/30370601930

Refactor

✅ refactor lint — passed

Deep dive: homeboy refactor lint data-machine --changed-since 2cb96b7

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-refactor-lint-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-refactor-lint-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/30370601930

Tooling versions

• Homeboy CLI: homeboy 0.321.0+192964f61a7e+e7ef7ed7
• Extension: wordpress from https://github.com/Extra-Chill/homeboy-extensions
• Extension revision: c75e1822
• Action: unknown@unknown