fix: support Harness rc.7 keyed settings slots

[GXX182]

What changed

• register the settings.plugin.item contribution with key: 'vision-bridge'
• extend the local slot registration type with the keyed-slot field
• add a regression test for the Host settings namespace key
• rebuild the committed browser bundle and source map
• bump the package version to 0.2.1

Why

Harness 0.1.0-rc.7 changed settings.plugin.item to a keyed slot. The plugin still supplied the legacy id field, so the client loader rejected the bundle with keyed slot "settings.plugin.item" requires options.key and the Plugins page could not load.

Impact

Version 0.2.1 loads on Harness rc.7 and routes its Image understanding settings card under the vision-bridge Host settings namespace.

Validation

• npm run lint
• npm run typecheck
• npm test — 9 files, 50 tests passed
• npm run build
• npm run publint
• npm pack --json — generated dsh-vision-bridge-0.2.1.tgz