claude: add Claude Code configuration, hooks, and skills

Summary

• CLAUDE.md: development instructions, conventions, architecture docs, and environment setup
• PostToolUse hook: auto-runs update-hash when editing software/*/ files
• Environment template: .claude/env.local.json.example for machine-specific paths

Skills

Skill	Description
/run-sr-test	Run a software release integration test in the background with environment setup, pre-flight checks, and result analysis
/test-results	Fetch test results for a git commit from ERP5's test_result_module
/deploy-instance	Deploy a new SlapOS instance: inspects the schema, generates a request script, executes it, and verifies deployment
/show-instances	List deployed instances for a software release with their connection parameters
/export-request-scripts	Generate request scripts for all top-level instances from the SlapOS proxy database

Test plan

• Verify skills appear in /skills list within Claude Code
• Run /run-sr-test rapid-cdn test.TestMasterRequest to verify it loads correctly
• Run /show-instances erp5-mcp-hateoas to verify it loads correctly
• Edit a software/*/ file and verify the hook triggers update-hash