docs: record runtime external package smoke

[ArcueidMP]

Summary

• Record Step 10.4 packaged Runtime external generated package load smoke as passed
• Update dev-log with the generated package path, Runtime exe path, and manual smoke result
• Update the Runtime unpacked packaging workflow with the latest external package smoke result
• Add a small packaging evidence note to release-readiness docs

Scope

Docs-only.

This PR does not:

• package Maker
• bundle Python
• package the Python image pipeline
• create an installer
• create NSIS setup
• create a portable single exe
• publish artifacts
• create a GitHub Release binary
• create or modify tags
• create a release
• add auto-updater support
• add zip export
• add persistent settings
• add Runtime launch-from-Maker
• add rembg
• add cloud APIs
• add system tray
• add multi-pet support
• add plugin support
• add new animation features

Verification

• git diff --check
• Hidden control character scan
• corepack pnpm typecheck

Step 10.4 result

Packaged Runtime external generated package smoke passed on 2026-05-28.

Passed:

• generated package contained pet.json, spritesheet.png, and preview.gif
• pet.json referenced spritesheet.png
• packaged Runtime launched
• Load Pet... opened the folder picker
• generated external package loaded
• generated pet displayed and animated
• drag, Reset Position, Always on Top toggle, and Exit worked

No release artifact was committed.