feat: add Checklist Inspector prompt-based checklist creation

[nathanhuh]

Summary

Extend Checklist Inspector so users can add checklist content from an in-TUI prompt instead of only loading YAML files manually.

Details

• Add an action menu or keybinding in Checklist Inspector that opens a prompt for adding checklist content.
• Prompts should be based on the current Checklist Inspector rulesets rather than free-floating text.
• Support all existing checklist rule types in internal/inspector/checklist.go: rds, security_group, secret, hosted_zone, route53_record, vpc, subnet, cloudwatch_log_group, cloudtrail_baseline, guardduty_baseline, config_baseline, and elasticache_valkey_baseline.
• For each ruleset, present predefined prompt fields that map to the YAML schema. For example, security group prompts should ask for inbound/ingress expectations such as required or forbidden rules.
• Persist generated checklist entries to the existing checklist-file flow/location instead of keeping them session-only.
• Preserve the current file picker and --checklist <path> behavior; prompt-based creation should be additive.
• Generated YAML should continue to load through the existing LoadChecklist validation path so unknown fields and malformed values are caught consistently.
• Update help/keybinding text for Inspector mode, Checklist Inspector results, and Checklist Inspector detail screens as needed.

Checklist

• Define prompt templates for each supported checklist rule type.
• Add Checklist Inspector action/menu/keybinding entry points.
• Implement prompt state and validation in internal/app/.
• Generate YAML entries compatible with internal/inspector/checklist.go.
• Persist new checklist content through the existing checklist file location/picker model.
• Re-load or re-run the checklist after saving so users see the new result flow.
• Add tests for prompt field mapping, persistence, validation failures, and screen transitions.
• Update README/docs for the new prompt-based checklist workflow and keybindings.