feat: add comprehensive pdd setup prompts for all LLM providers (#480)

[niti-go]

Summary

This PR adds 7 new prompt files to transform pdd setup into a comprehensive system bootstrapper that supports dynamic provider discovery, smart API key management, local LLM configuration, and interactive model selection with cost transparency across all LLM providers.

Closes #480

Changes Made

New Prompts Created

• pdd/prompts/setup_tool_python.prompt - Main orchestrator for the enhanced setup flow with menu-driven configuration
• pdd/prompts/api_key_scanner_python.prompt - Dynamic provider discovery from llm_model.csv, scanning all sources (.env, shell, api-env files)
• pdd/prompts/api_key_validator_python.prompt - API key validation using llm_invoke() instead of hardcoded HTTP requests
• pdd/prompts/provider_manager_python.prompt - Add/remove providers with atomic CSV updates and smart key storage
• pdd/prompts/model_selector_python.prompt - Interactive model selection with cost transparency and tier guidance
• pdd/prompts/local_llm_configurator_python.prompt - Configure Ollama, LM Studio, and custom providers
• pdd/prompts/pddrc_initializer_python.prompt - Initialize .pddrc with sensible project defaults

Example Code Files

• context/api_key_scanner_example.py - Example implementation showing multi-source key discovery
• context/api_key_validator_example.py - Example showing llm_invoke-based validation
• context/provider_manager_example.py - Example of CSV management and key storage logic
• context/model_selector_example.py - Example of tier-based model selection UI
• context/local_llm_configurator_example.py - Example of Ollama/LM Studio auto-detection
• context/pddrc_initializer_example.py - Example .pddrc generation

Documentation Updated

• README.md - Updated setup command documentation to reflect new capabilities
• SETUP_WITH_GEMINI.md - Updated to reference new multi-provider setup flow
• docs/ONBOARDING.md - Updated setup instructions for new user experience
• docs/SETUP_GUIDE.md - New comprehensive setup guide documenting all menu options and workflows
• pdd/docs/prompting_guide.md - Added guidelines for setup-related prompts

Key Features

Dynamic Provider Support

• Reads all providers from llm_model.csv instead of hardcoded list
• Supports Anthropic, OpenAI, Google, Fireworks, Groq, Vertex AI, and any future CSV additions
• No code changes needed when new providers are added to CSV

Smart API Key Management

• Scans keys from all sources: shell environment, .env files, ~/.pdd/api-env.* files
• Shows key source transparency (e.g., "✓ Valid (shell environment)")
• Smart storage: only saves to api-env.* if key was entered during setup (avoids duplicating keys from Infisical, .env, etc.)
• Safe removal: comments out keys instead of deleting (preserves ability to recover)

Interactive Model Selection

• Groups models by tier (Fast/Cheap, Balanced, Most Capable)
• Shows cost information ($1-5M vs $15-75M per million tokens)
• Smart defaults with opt-in for premium tiers
• Explains --strength parameter for runtime model selection

Local LLM Support

• Auto-detects Ollama and LM Studio installations
• Queries Ollama API for installed models
• Supports custom base URLs for other local providers
• Guides through adding models without API keys

Menu-Driven Flow

What would you like to do?
  1. Add or fix API keys
  2. Add a local LLM (Ollama, LM Studio)
  3. Add a custom provider
  4. Remove a provider
  5. Continue →

Review Checklist

• Prompt syntax is valid (all prompts follow PDD conventions)
• PDD conventions followed (includes, requirements, examples)
• Documentation is up to date (README, SETUP_GUIDE, ONBOARDING)
• Example code demonstrates key functionality
• All 7 prompts have corresponding example implementations

Next Steps After Merge

1. Regenerate code from prompts in dependency order:

   # No sync order script needed - these are new modules
   pdd gen pdd/prompts/api_key_scanner_python.prompt
   pdd gen pdd/prompts/api_key_validator_python.prompt
   pdd gen pdd/prompts/provider_manager_python.prompt
   pdd gen pdd/prompts/model_selector_python.prompt
   pdd gen pdd/prompts/local_llm_configurator_python.prompt
   pdd gen pdd/prompts/pddrc_initializer_python.prompt
   pdd gen pdd/prompts/setup_tool_python.prompt

2. Run tests to verify functionality:

   pytest tests/test_setup_tool.py

3. Test the new setup flow:

   pdd setup

4. Update llm_model.csv if needed to ensure all providers have required metadata (cost fields)

Risk Mitigation

• Atomic CSV updates: All CSV modifications use temp files + atomic rename
• Smart key storage: Never overwrites existing keys in environment
• Safe deletion: Comments out keys instead of deleting permanently
• Source transparency: Clear indication of where each key comes from
• Backward compatibility: Existing ~/.pdd/ configurations continue working

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Created by pdd change workflow (Step 13/13)