Summary

This PR fixes critical unbounded retry loops in Turtle._createCache() and Turtle.updateCache() that can cause infinite loops and browser hangs when canvas container bounds are never available. It also consolidates duplicated retry logic across turtle.js and block.js into a shared, well-tested utility.

Problems Fixed

1. Unbounded retry in Turtle._createCache() (infinite loop)

The original code called setTimeout(() => this._createCache(), 200) with no maximum retry limit. If container.getBounds() never returns a value (e.g., due to a rendering failure or detached container), this loops forever, consuming memory and CPU.

2. Broken promise chain in Turtle.updateCache() (silent failures + infinite recursion)

• The recursive this.updateCache() call was neither awaited nor returned, so failures were silently swallowed
• No retry limit — infinite recursion if bounds stays null
• Logged "Block container" instead of "Turtle container" (copy-paste bug)

3. Code duplication across turtle.js and block.js

Three separate hand-rolled retry implementations existed with inconsistent patterns. block.js already had bounded retries with exponential backoff, but turtle.js did not.

Changes

Before / After

Turtle._createCache() — Before

_createCache() {
    this.bounds = this.container.getBounds();
    if (this.bounds == null) {
        setTimeout(() => {
            this._createCache();
        }, 200); // ← No limit. Runs forever.
    } else {
        this.container.cache(this.bounds.x, this.bounds.y, this.bounds.width, this.bounds.height);
    }
}

Turtle._createCache() — After

_createCache() {
    return retryWithBackoff({
        check: () => {
            this.bounds = this.container.getBounds();
            return this.bounds;
        },
        onSuccess: (bounds) => {
            this.container.cache(bounds.x, bounds.y, bounds.width, bounds.height);
        },
        maxRetries: 20,
        initialDelay: 50,
        errorMessage: "Turtle._createCache: could not get container bounds after 20 attempts"
    });
}