Add comprehensive documentation structure with GitHub Copilot integration

[Copilot]

Establishes authoritative project guidelines for developers and AI agents. Implements three-tier documentation with GitHub Copilot custom agents and skills following official specifications.

Documentation Structure

Three-tier hierarchy:

• Level 1: README.md - Quick start and feature overview
• Level 2: CONTRIBUTING.md - Development workflow, standards, testing
• Level 3: docs/part-2-1-always-on-instructions.md - Comprehensive reference (527 lines)

Navigation: docs/README.md provides indexed access by audience and topic

GitHub Copilot Integration

Custom Agent: .github/agents/feature-builder.md

---
name: feature-builder
description: AI agent specializing in building new features for Three Rivers Bank...
tools: ["read", "edit", "create", "search", "npm", "mvn", "git", "bash"]
infer: true
---

Persona-driven agent with React + Spring Boot expertise, complete feature workflows, and success criteria.

Agent Skill: .github/skills/create-agent-skill/SKILL.md

---
name: create-agent-skill
description: Create new GitHub Copilot agent skills following agentskills.io specification
license: MIT
---

Enables skill creation following agentskills.io spec with templates and validation.

Enhanced Instructions: .github/copilot-instructions.md now references complete documentation hierarchy.

Always-On-Instructions Content

docs/part-2-1-always-on-instructions.md covers:

• Architecture principles: H2 primary, BIAN supplementary, circuit breaker patterns
• Coding standards: Java/Spring Boot, React/MUI, complete examples
• API patterns: REST endpoints, DTOs, resilience
• Testing conventions: JUnit, Playwright, multi-viewport
• Deployment: Docker, Azure Container Apps, CI/CD
• Security practices and troubleshooting

Key Patterns

Backend example:

@CircuitBreaker(name = "bianApi", fallbackMethod = "fallbackToH2Data")
@Retry(name = "bianApi")
public BianResponse callBianApi(Long cardId) {
    return bianApiClient.getCardData(cardId);
}

Frontend example:

const { data: cards, isLoading, error } = useQuery({
  queryKey: ['cards'],
  queryFn: fetchCards,
  staleTime: 5 * 60 * 1000,
});

Stats

• 1,965+ lines of documentation across 9 files
• 6 new files, 3 updated
• Full agentskills.io and GitHub Copilot spec compliance
• All cross-references validated

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Update and improve project instructions per always-on-instructions guidance</issue_title>
<issue_description>## Requirement

Create, update, and refine the best instructions for this repository, explicitly using the recommendations from the always-on-instructions file as the authoritative source for foundational Copilot configuration. This will:

• Centralize and standardize project management knowledge
• Clarify onboarding workflows and best practices
• Make improvements easier to validate, document, and maintain

Tasks:

1. Identify current documentation and instructions used in this repo
2. Compare and integrate guidance from the attached always-on-instructions file (docs/part-2-1-always-on-instructions.md) from customize-your-repo as the baseline reference
3. Draft improved instructions (README, workflow docs, contribution guidelines, etc.)
4. Include the referenced create-agent-skill skill from customize-your-repo in .github/skills/create-agent-skill/ following agentskills.io specification
5. Create and include the Feature Builder custom agent from customize-your-repo in .github/agents/feature-builder.md following documented guidelines for custom agents
6. Review with project stakeholders and validate changes
7. Roll out updates and monitor for further improvements

This issue will track planning, progress, and implementation steps for updating project instructions to ensure alignment with Copilot best practices.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Update and improve project instructions per always-on-instructions guidance #19

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