Prevent stack overflow crashes with recursion limit

[rickhohler]

This PR addresses a missing safety mechanism in TOONEncoder where deeply nested structures could cause a stack overflow crash.

Changes

• Added recursionLimit: New property on TOONEncoder (default: 1000).
• Depth Checking: Implemented depth checks in Keyed, Unkeyed, and SingleValue encoding containers.
• Error Handling: Instead of crashing, the encoder now throws EncodingError.invalidValue if the recursion limit is exceeded.

Verification

• Enabled testDeepRecursion in BugHuntingTests which confirms that the encoder now throws a catchable error instead of crashing the process.

Note: testValueFromDictionaryKeyOrder and testNegativeZeroEncoding in BugHuntingTests will fail on this branch as they depend on the fixes in PR #20 (Serialization Correctness). This is expected isolation.

[mattt]

Thanks for opening this PR, @rickhohler! Left some comments with suggested changes.

[mattt]

Thanks for your help with this, @rickhohler! I worked through the remaining feedback and adjusted the recursion limit to 32, matching the decoding limit.