feat: Gold Standard maintenance and automation suite

[lynnwallenstein]

Description

This PR implements a comprehensive suite of maintenance, automation, and project quality tools to ensure a 'Gold Standard' experience for both the generator repository and its scaffolded project templates.

🚀 Key Improvements

1. Engine & Environment Hardening

• Dynamic Root Resolution: Scripts like start-container.sh now resolve the project root correctly regardless of where they are called.
• Improved Setup Workflow: Replaced manual GitHub Token prompts with a secure gh auth login workflow.
• Diagnostic Tooling: Added troubleshooting.sh to diagnose and fix common environment issues (permissions, missing .env, placeholders).
• Hardened Parsing: boot-check.sh now uses robust parameter expansion for trimming values, supporting spaces in variables (e.g., Git names).

2. Quality Gates & CI/CD

• E2E Install Verification: Automates the testing of install.sh to ensure the scaffolded project structure remains intact and isolated.
• Devcontainer Build Checks: CI now validates that both the root and template Docker/Devcontainer configurations build successfully.
• Shell Linting: Integrated shellcheck across all scripts with a corresponding GitHub Action.
• Formatting Enforcement: Added prettier for repository-wide formatting (Markdown, JSON, YAML) with CI checks and a make format target.
• Dependabot: Enabled automated dependency tracking for GitHub Actions and Docker base images in both root and templates.

3. Documentation & AI Standards

• AI Agent Boundaries: Clear instructions in README.md and AGENTS.md to guide AI assistants on where to learn (payload) and where to develop (engine).
• Consistency Audit: Performed a final polish to fix documentation drift and ensure path consistency across all scripts and guides.

🛠 Tools Added/Updated

• shellcheck: Script linting.
• prettier: Code formatting.
• devcontainers/ci: Build verification.
• gh cli: Primary authentication mechanism.

How Has This Been Tested?

• Verified via GitHub Actions (E2E, Shellcheck, Prettier, Builds).
• Manual verification of install.sh and troubleshooting.sh in clean environments.
• Root repository linting and formatting via make lint.