my work bases overtime on a 40 hour week that starts on saturday.

I just came off of a 10 day stretch of work.

My schedule:
I started on monday the 2nd and worked 8-5 through saturday the 7th.
Sunday the 8th, I had to come in for a scheduled meeting. I clocked in for 3 hours. My HR manager said it was a scheduled shift. I continued to work on monday the 9th (8-5) through Wednesday the 10th. I was scheduled to work on Thursday the 11th, but they pulled me from the schedule because of the stretch of days.

I'm curious if the overtime rule applies (time and a half for the first 8 hours following the seventh day and double time for any hours after that). It's a bit fuzzy because the meeting wasn't a full 8 hour shift. Is that considered a work day? If so, that would be 10 consecutive days in a row that I worked.

Shifts and schedules are legally meaningless. Under federal law (FLSA) the work week starts at exactly the same day and time each week. It is possible for the employer to have different workweeks for each employee or group of employees but that would be logistically very difficult to manage. The law also expects the workweek to be largely fixed and has some fairly burdensome requirements on the employer when they try to change the workweek. The last two employers I worked for had a "workweek" ending Sunday midnight even though these were large companies with a lot of employees in many states with many different shifts and schedules.

CA has the "workday", but that is a function of the federal workweek. Any day one works is a workday under CA rules, no matter how little time worked. You can find the CA OT rules below. You might trying pressing the hotkey definitions for workday and workweek on that website.

http://www.dir.ca.gov/dlse/FAQ_Overtime.htm