[amariichi]

What changed

• Keep Looking Glass click-selected focus locked until Resume Auto, except when scene or near-plane safety requires recovery.
• Require a second same-area click for unusually distant focus selections.
• Drive Looking Glass automatic depth placement from the source area currently visible after zoom and pan.
• Retain full-frame near-plane protection independently of viewport focus statistics.
• Add regression coverage and update bilingual user/technical documentation.
• Bump the Python and frontend versions to 1.3.0.

Why

Looking Glass users can inspect a cropped part of the source, so off-screen depth should not continuously move the visible subject. Manual focus also needs to remain stable across long shots without allowing an accidental distant click or a scene cut to leave the display black.

Scope

The new placement behavior is gated to Looking Glass Pinhole + Auto Source View. SBS, monitor, generic WebXR, Free Orbit, and Creative Relief retain their existing behavior.

Validation

• 118 frontend tests
• ESLint
• Production frontend build
• Locked backend lint, compile, and tests
• git diff --check
• Physical Looking Glass Go validation

Release

This PR prepares VideoDepthViewer3D v1.3.0. After PR CI and post-merge main CI pass, the merge commit will receive annotated tag v1.3.0 and a GitHub Release.