Remove CallableTaskFactory indirection from CallableTaskBuilder

[mdproctor]

Summary

• Replaces the two-step init() → CallableTaskFactory.get() pattern on CallableTaskBuilder with a single build() method that returns CallableTask directly
• Deletes the CallableTaskFactory interface from the public API
• Updates all six implementations and the CallTaskExecutor call site

Motivation

CallableTaskFactory is a Supplier<CallableTask> whose .get() is called immediately after init() returns — no implementation uses the deferred construction. Every implementation already captures all state in the lambda closure returned from init(), so the factory layer adds a public type, an allocation, and a concept to the API surface with no behavioral benefit.

After this change:

• Smaller public API — one fewer type for implementors to learn and maintain. Third-party CallableTaskBuilder implementations (e.g. in Quarkus Flow) drop the factory wrapper and return CallableTask directly.
• Simpler call site — CallTaskExecutorBuilder stores a CallableTask directly instead of holding a factory and deferring .get().
• No behavioral change — same data in, same CallableTask out. All existing tests pass.

Test plan

• mvn verify — all 232 tests pass (one pre-existing flaky SchedulerTest.testAfter timing test passes on rerun)
• No remaining references to CallableTaskFactory in the codebase

🤖 Generated with Claude Code