Day 1 patch based on immediate feedback.

- Added an additional page explaining ventilation ducts in the guide textbook

- Added a mission briefing document to accompany the textbook with additional visuals

- Made both the textbook and mission briefing document available in the security office

- Added a brief screen overlay and auditory cue when a task has been completed

- Added directional wall markers

- Tweaked the ramping frequency of hostile entities

- Fixed a bug where pausing while interacting with certain mechanics broke the inventory

A few additional features I plan on adding to the demo include a visible health indicator and a few more "ghost" encounters, bar I get any additional recommendations for this version.