Streamline README and document UX improvement opportunities

[Copilot]

Addressed request to clean up README and create UX improvement documentation.

Changes

README.md - Reduced from 304 to 139 lines (54%):

• Consolidated redundant sections and verbose descriptions
• Promoted modern CLI interface (pnpm start provider:model) to primary usage
• Tagged legacy interfaces: environment variable execution, DEBUG_MODE, v1 utilities
• Streamlined provider list to reference .env.example instead of duplicating

suggestions.md - New file with 18 prioritized UX improvements:

• Simplification: Deprecate legacy interfaces, simplify provider config, default to help message
• Features: Interactive selection, cost estimation, preset configs, progress indicators
• Quality: Config validation, strict TypeScript, automated setup testing
• Priority tiers: 4 high (quick wins), 4 medium (good ROI), 4 low (nice-to-have)

Before:

# Multiple confusing ways to run
pnpm start                          # Runs ALL providers
PARALLEL_EXECUTION=true pnpm start  # Legacy env var
pnpm start anthropic:claude-3-haiku # New CLI

After (in suggestions.md):

# Single clear interface
pnpm start                          # Shows help
pnpm start anthropic:claude-3-haiku # Explicit provider:model
pnpm start --preset fast            # Proposed preset system

Legacy features remain functional but are clearly marked for eventual deprecation.

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[maxffarrell]

Include openrouter example