Restore machine discovery of the PHP SDK conformance authority from the platform suite

[rmcdaniel]

Problem

Platform conformance suite version 37 is current and byte-equivalent between Workflow 2.0.0-rc.8 and the live docs site, but the suite no longer exposes the structured PHP SDK conformance authority relationship that earlier public work established. The standalone PHP authority remains published and linked from human discovery pages, while its URL and schema are now known only to site tooling rather than to a machine consumer starting from https://durable-workflow.com/platform-conformance-contract.json.

This regresses machine discovery: following the root suite alone cannot locate or identify the stable PHP SDK contract, even though that contract points back to the suite.

Acceptance criteria

• The public root suite exposes a structured, schema-defined relationship to the stable PHP SDK conformance authority, including its consumer-resolvable URL, schema identity, version, and status.
• The Workflow package authority and live docs authority remain byte-equivalent.
• Human and model discovery surfaces derive from or validate against the same public relationship; a tooling-only hard-coded registry is not the sole source of discovery.
• Qualification fails if the root relationship is removed, disagrees with the standalone PHP contract, or points at a non-public resource.
• Existing checks that reject source-tree, filesystem, and internal harness details in the standalone contract remain effective.

Delete when

Delete when a consumer starting only from the live platform suite can deterministically discover and validate the stable PHP SDK conformance contract, and qualification prevents the relationship from being removed or drifting.

Required source targets

durable-workflow/durable-workflow.github.io@main
durable-workflow/workflow@v2

[rmcdaniel]

Completed in 6542094b6ae2 on main.

No package release was required for this source-only change.

Required public qualification passed: https://github.com/durable-workflow/durable-workflow.github.io/actions/runs/30595766850

[rmcdaniel]

Cross-repository landing evidence (generated from trusted implementation pull requests or authenticated protected-branch completion records):

Target	Latest attempt	Bound provenance	Landing	Required qualification	State
durable-workflow/durable-workflow.github.io@main	Not linked	Pending	Pending	Pending: Executable documentation contracts; required: Executable documentation contracts	pending:no-linked-pull-request
durable-workflow/workflow@v2	Not linked	Pending	Pending	Pending: build; required: build	pending:no-linked-pull-request

The parent remains open until every declared target is complete.