feat: Add Step Local Memory (#134), Generation ID Protection (#128), and While Loop Breakpoint Support (#166)

[jagannalla]

Description

This PR addresses three core enhancement and bug-fix issues across Maestro's runtime, engine, and database layers:

1. Step Local Memory Support (Maestro add local-memory support #134):

   • Added transient, step-instance-scoped local memory with a strict capacity constraint of 64KB (serialized JSON bytes).
   • Integrated lifecycle hooks in MaestroTask to ensure local memory is cleared when the step terminates or is canceled.
   • Exposed getLocalMemory() in StepRuntimeSummary for child step execution contexts to read/write.

2. Generation Guard Data Protection (Leverage generation_id to prevent reverting step data #128):

   • Added a generation_id column to the maestro_step_instance schema (migration included).
   • Enforced database-level protection checks on step updates/upserts, preventing stale flow executions/workers from overwriting updates from newer runs (generation_id <= EXCLUDED.generation_id and generation_id <= :flowGeneration).
   • Propagated flow generation context from the event loop down through database synchronization layer.
   • Preserved backwards-compatible signatures to prevent breaks in legacy tests and services.

3. Human-in-the-Loop While Loop Breakpoint Support (Human in the loop support for while loop #166):

   • Added PAUSED to the StepRuntime.State state machine, allowing step execution to yield back a pause state.
   • Updated StepRuntimeManager to handle PAUSED step status by cleanly calling runtimeSummary.markPaused(...).
   • Updated WhileStepRuntime to check stepBreakpointDao.createPausedStepAttemptIfNeeded(...) between iterations. If a breakpoint exists, it yields a PAUSED state with timeline event logs.
   • Modified WhileStepRuntime.start(...) to return the existing WhileArtifact directly, allowing a seamless resume from the same attempt/iteration without resetting counters or the inner loop's run policy.
   • Wired database breakpoint DAO dependency in MaestroStepRuntimeConfiguration.

Verification

• Unit and Integration Tests: Added extensive test coverage for all three features. Verified with ./gradlew :maestro-engine:test (all pass).
• Compile/Build Checks: Verified compilation and formatting with ./gradlew build -x test and ./gradlew spotlessCheck.