[EPIC 6.0] Extension Privacy Features


## Problem

Privacy-preserving RPC management for extension.

## Success Criteria

- [ ] RPC hijacking for custom providers
- [ ] Privacy-preserving redirection

## Non-goals

Mobile browsers, browser-native key storage, standalone mode

## Timeline

Q1 2026 - Q2 2026

## Dependencies

**BLOCKED BY:** Epic 1

## Notes

Extension stability (#16, #26) in Epic 1. This covers privacy features.