Fixes #337

While using a monitor, the camera controls were still reaching Minecraft's normal interaction code. Looking down and holding left click could break the camera or another block, and held right click could activate the camera and print its status in chat.

This keeps camera mode isolated in three small pieces:

• consume left- and right-mouse events only while the camera overlay is active
• stop cancelable player interactions from reaching blocks, entities, or items while viewing a camera
• hide the player's hand during the camera view

The hand-rendering change is deliberately kept in its own commit (a7867571), so it can be dropped or reverted independently if that visual change is not wanted.

I left the existing camera polling behavior alone. Zoom and exit still use the same short hold, including the startup delay that prevents the click used to open the monitor from immediately closing it again. Laser-camera firing remains on the Space key and its packet path is unchanged.

Tested with Forge 1.12.2:

• reproduced the block breaking on the original jar
• confirmed camera controls no longer affect blocks or print camera status in chat
• confirmed normal interaction returns after leaving the camera view
• verified the laser-camera Space-key targeting path is unchanged
• built successfully offline with Java 8 (test NO-SOURCE)