Polish frozen toolbar annotations for 0.1.2

[yvette-carlisle]

Summary

• keep frozen annotation toolbar size stable when second-row style controls are shown
• make arrow thickness controls effective and set the shared brush/arrow default to 3
• add spotlight border color and width controls, defaulting width to 0 for no border
• bump workspace, staged app fallback, and release docs to 0.1.2

Validation

• cargo check --workspace --all-targets
• cargo make fmt-swift-check
• cargo make build-swift-strict
• cargo make test-macos-native-host-stage
• cargo make fmt-toml-check
• git diff --check
• semantic drift audit: pass, no stale phrase hits
• staged Rsnap.app CFBundleShortVersionString and CFBundleVersion: 0.1.2