fix(turtles): Clear intervals when removing turtles to prevent memory…

[WillyEverGreen]

Description

Fixes a memory leak where intervals created by MeterActions.onEveryBeatDo() were not cleared when turtles were removed.

Problem

When a turtle with an active "On Every Beat Do" interval is deleted, the setInterval continues running as a "zombie" interval, causing:

• Memory leaks in long-running sessions
• Potential performance degradation
• Unexpected behavior from orphaned interval callbacks

Solution

Added interval cleanup logic to [removeTurtle()] in [js/turtles.js]:

• Check if the turtle has an active interval property
• Clear it with clearInterval() before removal
• Set turtle.interval = undefined for clean state

Testing

• npm run lint
• npm test
• Manual verification: Create turtle with "On Every Beat Do" block, delete turtle, confirm interval is cleared

Impact

• Prevents memory leaks during normal usage
• Improves stability in extended sessions
• No breaking changes

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.