Export net worth and investment account values

[cbangera2]

What changed

• adds separate Net Worth History and Investment History CSV choices to the extension popup
• fetches Credit Karma's persisted net-worth and investment GraphQL datasets
• exports the complete All graph series, filtered to the selected date range, with one value per date
• preserves the newer transaction category and pagination behavior from main
• updates extension metadata and documentation for version 2.1
• adds parser, CSV, and manifest tests plus a hardened validation/package CI workflow
• adds contributor guidance for safely recording sanitized HAR files
• adds repository instructions requiring transparent disclosure of LLM-assisted pull requests

User impact

Users can export the values behind both wealth graphs directly to separate CSV files instead of trying to scrape rendered charts.

Validation

• node --test (6 tests passing)
• node --check background.js
• node --check content.js
• node --check popup.js
• verified against the supplied HAR response shapes (406 net-worth values and 402 investment values, all numeric)
• GitHub Actions validation and packaging jobs pass

AI assistance

This pull request was implemented with OpenAI Codex. The maintainer directed the feature scope, product decisions, documentation wording, and PR updates. Automated tests, syntax checks, HAR-shape validation, and GitHub Actions passed. The final extension behavior has not been manually tested by a human in Chrome as part of this PR workflow.

Closes #6