feat(errors): typed per-operation error hierarchy

[ayushiahjolia]

Issue #, if available: #120

Description of changes:

Replaces the single catch-all CallableRuntimeError with a typed, per-operation error hierarchy. A failed step, invoke, child context, or wait_for_condition now surfaces as a distinct, catchable exception type. It also lands the from_exception/throw_if_error changes those types require. The CallbackError rework and the nested-boundary regression test are intentionally deferred to follow-up PRs.

Breaking changes

• Operation failures now raise the typed subclasses instead ofCallableRuntimeError (removed).
• error_type holds the operation discriminator (e.g. "StepError"), not the original Python exception name; the original is available via the message and, on the first run, __cause__.
• wait_for_condition check failures are now wrapped in WaitForConditionError rather than re-raised raw.
• An exhausted interrupted step fails immediately as StepError rather than round-tripping through a Lambda retry.

Testing

• Updated/added unit tests across exceptions, lambda_service, state, concurrency, and the four operation handlers.
• Added coverage for: registry + from_error_fields (including fallback), from_exception field preservation and single-level cause-walk,raise_operation_error, wait_for_condition control-flow errors propagating unwrapped, and the step FAIL checkpoint recording the StepError discriminator.
• Added integration test and example.

Follow-ups

• Move CallbackError under DurableOperationError with graded subclasses (CallbackExternalError, CallbackTimeoutError, CallbackSubmitterError) and drop CALLBACK_ERROR metadata.
• Regression test for data surviving ≥2 nested run_in_child_context boundaries

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