[Feature in SDK]: add Bitrix24 SDK developer skill

[mesilov]

Description

Add a dedicated Bitrix24 SDK developer skill for product teams that use bitrix24/b24phpsdk in their own applications.

This skill must focus on how to write product code with the SDK: initialization, webhook/OAuth usage, service access, result handling, pagination/batch usage, exception handling, testing strategy, and common mistakes. It must not replace the existing maintainer skill, which remains focused on repository issue/PR/release workflows.

Requirements

• The skill must be discoverable by Claude Code as a project skill.
• The skill must be discoverable by Codex as a project skill.
• The skill must be distributable through llm/skills from https://github.com/roxblnfk/skills.
• The SDK package must expose the distributable skill through the donor-side composer.json extra.skills.source contract used by llm/skills.
• The distributable skill source must avoid shipping the repository maintainer workflow skill to SDK consumers.
• The skill content must explain SDK usage from the perspective of product application development, not SDK internals maintenance.

Implementation plan summary

The working plan is tracked in .tasks/562/plan.md.

• Canonical distributable skill source: resources/skills/b24phpsdk-developer/.
• Claude Code project loader: .claude/skills/b24phpsdk-developer/SKILL.md.
• Codex project loader: .agents/skills/b24phpsdk-developer/SKILL.md.
• Composer distribution metadata: add composer.json extra.skills.source = "resources/skills".
• Validation includes quick_validate.py, Composer validation, repo lint/unit gates, and an empty-project smoke test.
• Smoke test creates a temporary Composer project, installs the SDK from the implementation branch, installs llm/skills, runs composer skills:update bitrix24/b24phpsdk, verifies .agents/skills and .claude/skills, then runs a PHP hello-world script that reads Bitrix24 CRM contacts through the SDK.

Distribution notes

llm/skills copies skill directories from Composer/vendor packages into a consumer project's configured skill directory. A donor package declares a source directory with:

{
  "extra": {
    "skills": { "source": "resources/skills" }
  }
}

Consumer projects can sync skills into .agents/skills and mirror them to Claude Code with aliases such as .claude/skills.

Verification

• Create an empty temporary project directory.
• Install bitrix24/b24phpsdk as a Composer dependency from the implementation branch.
• Install or otherwise make available the llm/skills Composer plugin/command.
• Run the skill installation command from the temporary project so the SDK skill is installed as a project skill.
• Verify the installed skill is visible in the Codex-compatible project skill path.
• Verify the installed skill is visible in the Claude Code-compatible project skill path.
• In the temporary project, create a minimal hello-world PHP CLI project that follows the installed skill and uses bitrix24/b24phpsdk to read contacts from Bitrix24.
• Run the hello-world script against a configured Bitrix24 webhook and verify it receives a contacts response from Bitrix24.

Example

No response