feat(extension): idstack Chrome Extension experiment for Canvas & Docs

[savvides]

Summary

Brings idstack's evidence-based course design audits to educators and instructional designers outside the terminal via a native Manifest V3 Chrome Side Panel.

• Frictionless Workflow: Zero IT integrations, zero developer console setups, zero required signup.
• Canvas LMS & Google Docs Support: Extracts course context directly from open tabs.
• Evidence-Grounded Audits: Classifies Bloom's Revised Taxonomy levels, checks constructive alignment, and renders findings with T1–T5 evidence badges from 108 research studies.
• 1-Click Actions: Instant clipboard copy for rewritten elaborated rubrics/objectives, built-in demo fallback mode, and settings drawer for optional BYOK API keys.
• Publication Design System: Complies with DESIGN.md publication tokens.
• Test Coverage: All 6 extension test suites and master smoke test passing (356/356).