docs: add community PHP plugin SDK

[shoemoney]

Description

Adds the community-maintained PHP SDK beside the Go, .NET, and Python entries in the plugin SDK table.

Implementation: https://github.com/shoemoney/mcpd-plugins-sdk-php

The SDK uses the unchanged mcpd-proto v1 schema and generated PHP protobuf messages. Plugin authors extend a PHP BasePlugin; RoadRunner provides gRPC over TCP or Unix sockets. It implements all eight lifecycle, identity, health, and HTTP interception methods, with an executable launcher accepting mcpd's --address and --network flags.

Validation:

• PHP tests cover service signatures, pass-through behavior, binary protobuf round trips, and request-copy isolation.
• Mozilla's Python plugin client called all eight RPCs against the PHP worker over both TCP and Unix sockets.
• A local mcpd 0.5.3 daemon started with the PHP plugin configured as required; Paider discovered and called the time tool through its HTTP API.

The SDK README documents installation from source, RoadRunner and PHP pcntl requirements, plugin registration, and reproducible tests. It is not yet on Packagist and is described as community-maintained rather than Mozilla-maintained. This PR changes documentation only.

PR Type

• New Feature
• Bug Fix
• Refactor
• Documentation
• Infrastructure / CI

Relevant issues

None.

Checklist

• I understand the code I am submitting.
• I have added or updated tests that cover my change.
• I ran relevant checks locally (make lint, make test).
• Documentation was updated where necessary.
• I have read and followed the contribution guidelines.

Summary by CodeRabbit

• Documentation
  • Added a community PHP plugin SDK to the list of available plugin SDKs.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Organization UI

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Plan: Advanced

Run ID: 682ac5c7-7785-4b0d-bc44-4d5f29f5c953

📥 Commits

Reviewing files that changed from the base of the PR and between d865c69 and 11161d3.

📒 Files selected for processing (1)

• README.md

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Walkthrough

The README plugin SDK table now includes a community-maintained PHP plugin SDK repository.

Changes

PHP SDK documentation

Layer / File(s)	Summary
Add PHP SDK entry README.md	The mcpd plugin SDK table now lists the community-maintained PHP SDK repository.

Suggested reviewers: peteski22

Priority: ⬇️ Low — Defer this documentation-only update because it adds a community PHP SDK entry without changing public entities or product behavior.

Merge Risk: ⚪ Minimal · up to 11161

This change adds a community-maintained PHP plugin SDK to the README documentation table. It does not alter runtime behavior, configuration, or dependencies, and is ready to merge.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the documentation change: adding a community PHP plugin SDK.
Description check	✅ Passed	The description is relevant and mostly complete. It explains the change, identifies the documentation type, provides validation details, and states that the PR changes documentation only. The AI Usage…

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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