Release Compass 0.3.20

[forhappy]

Summary

• Bump the Compass workspace and internal package metadata to 0.3.20.
• Align the VS Code package metadata and qualification producer with 0.3.20.
• Move the pending user-facing changes into the 0.3.20 changelog section dated 2026-08-24.

Release highlights

• Grounded Agent Graph overlays with citation-backed operations, immutable revisions, exact rebase, and bounded audit.
• React/frontend graph hardening and the native architecture viewer projection.
• Native document artifacts with managed OCR and explicit platform behavior.
• Explicit semantic provider/model selection and qualifying Swift, Dart, Scala, and Groovy pipelines.
• VS Code Ask/Explain/CompassQL workbench and direct caller/callee graphs.

Validation

• cargo metadata --locked --no-deps --format-version 1
• cargo fmt --all -- --check
• sh scripts/check_product_boundary.sh
• sh scripts/test_release_scripts.sh
• JSON parsing, metadata consistency, and git diff --check
• Full platform builds and release qualification are intentionally delegated to the required GitHub Actions release/PR workflows for this remote-only release request.

The separate local Marketplace publishing workflow edit is not included in this PR.