Share compact homework review and public link controls

[alexeygrigorev]

Part of #308. The issue remains open through both site adoptions.

Shared controls

• Render one semantic, compact Review list with clear empty answers and Edit links, while keeping accepted and unsent draft snapshots separate. Long answers show a short preview with an expandable full answer.
• Add an assignment-cap-aware Learning in Public link editor with optional blank state, add/remove controls, accessible field labels, and newline-backed answer storage compatible with stepper autosave.
• Keep a visible textarea fallback so plain POST still works when JavaScript is unavailable.
• Keep host styling in each consumer; the package owns structure and behavior.

Verification

• uv run pytest -q tests/homework_steps/test_flow.py — 26 passed, including configured public links saved through the shared stepper and long-answer Review disclosure.
• make check — passed before the last template/test change; CI reruns it on the current head.
• Full local package suite on the preceding head: 2,221 passed, 3 skipped. CI reruns on the current head.

After package merge/release

• AISL and DTC adopt the shared partials and script, then verify browser journeys and run both consumer suites. Close Shared compact homework review and public-link controls #308 after those adoptions.