Document embeds Phase 1: finish Tasks 4-6

[avrabe]

Context

Branch feat/document-embeds has Tasks 1-3 committed (3 commits). Tasks 4-6 remain.

Spec: docs/superpowers/specs/2026-03-29-document-embeds-design.md (on docs/specs-and-plans branch)
Plan: docs/superpowers/plans/2026-03-29-embed-phase1.md

Completed (on branch)

• Task 1: EmbedRequest parser + error types (7 tests) — commit 3f24ad5
• Task 2: Stats + coverage HTML renderers (4 tests) — commit e69d0d3
• Task 3: Refactor render_to_html with embed_resolver closure (2 tests) — commit 71595c4
  • Note: needs build verification — syspolicyd was at 100% CPU preventing clean builds. Kill syspolicyd first: sudo kill -9 $(pgrep syspolicyd)

Remaining

• Task 4: rivet embed CLI command — Command::Embed variant, cmd_embed() handler (3 tests)
• Task 5: Export provenance stamps + dirty-tree warning — SC-EMBED-1, SC-EMBED-4 (3 tests)
• Task 6: E2E integration tests + Playwright regression (7 tests)

After Tasks 4-6

1. Run full test suite (cargo test && cargo clippy)
2. Squash commits and recommit in main checkout (worktree pre-commit hooks broken)
3. Create PR
4. Add Playwright E2E tests for embeds in documents

Key files

• rivet-core/src/embed.rs — parser, resolver, renderers
• rivet-core/src/document.rs — refactored render_to_html with embed_resolver closure
• rivet-cli/src/render/documents.rs — passes embed resolver to render_to_html
• rivet-core/src/export.rs — placeholder resolver (Task 5 adds provenance)