[ashtree74]

Prepare the local PreviewMD 1.9 (13) installer with the fixes merged in #30. Bump the app version/build and record the exact build source, final artifact hashes, Apple Accepted submissions, and delivery verification in docs/releases/PreviewMD-1.9-13.json.

The DMG and fallback ZIP were built from f8c4fdb23e758dd46b5d8c7dc15296dcfb6d84ab, signed with Astrography's Developer ID, notarized, and stapled. The application is retained under dist/releases/PreviewMD-1.9-13/; the previous 1.8 artifacts remain intact. This PR does not publish a GitHub Release or change the landing-page download.

The landing-page consistency test validates the public 1.8 installer against its release receipt, including its actual size and SHA-256, so preparing a newer local app does not incorrectly require a public download update.

Validation:

• Mounted final DMG: app and embedded Quick Look are 1.9 (13), Universal 2, macOS 14 minimum with SDK 27; all packaged renderer and legal files match the source.
• App, extension, and DMG code signatures verify; app and DMG stapler validation and Gatekeeper report Notarized Developer ID.
• Repo and requested additional DMG copies have identical SHA-256; receipt sizes/hashes/submission IDs match the actual outputs and Apple notarytool info responses.
• Property lists, JSON, shell syntax, diff whitespace, all 9 Python server tests and all 8 Node signup lifecycle tests pass. Full Swift tests and Universal 2 packaging passed on merged fix: improve native editing latency and fit expanded tables #30 main; the PR also runs CI.
• Independent review covers release metadata, source provenance, and preservation of the previous release.