Prepare PHP SDK 2.2.1 bounded dashboard helper

[rmcdaniel]

Prepare the exact PHP SDK 2.2.1 identity for the observer performance helper
merged in #99. This changes only release metadata. Worker protocol, execution
contracts and codecs are unchanged.

The implementation passes every normal PHP 8.1–8.4, Laravel 9–13, Symfony,
documentation and package gate. The final local transport suite passes 18 cases /
203 assertions with no skips; full PHPStan passes.

Before publication, pass the exact package identity check and normal source
gates. After publication, verify Packagist and registration identity, then
exercise the new method against the exact published Server image. Server's
additive route is being prepared in durable-workflow/server#305. Waterline
integration remains in durable-workflow/waterline#142 and its broader acceptance
issue #141 stays open.

[rmcdaniel]

PHP SDK 2.2.1 is published from 27e1b1409744e56d0ac7a8d6fec6b75df95b4960,
qualified tree a932fd1fe7f863c34993ce20f414285bc431a8e2. All source gates and
the fresh registry-only consumer pass, including 18 transport cases / 203
assertions with no skips. Packagist identity and worker registration are verified.
The merged branch was deleted and verified absent.

Server 2.5.3
is now published. A fresh SDK 2.2.1 install passes 13 actual HTTP checks against
index sha256:7c62b388802dda1922ada0a920ea8335c6a05ed3638741137cea4c8ba228bf22,
including one bounded read, namespace isolation, unknown audit counts, ordinary
full-audit compatibility and invalid-token refusal.
Published lifecycle verification
passes all 12 PHP/Python/Rust and operator cells with no findings.

This SDK helper is delivered. Waterline #141
remains open through its complete operator experience and published acceptance.