Add code assistant tutorial feature

[Rajkumar7633]

Description

This PR adds a new code assistant tutorial and improves code quality across the project.

New Features

• Added code-assistant tutorial module with 4 tools (generate, review, explain, debug code)
• Created CodeAssistant.java with comprehensive code assistance capabilities
• Added detailed README with setup and usage instructions
• Updated parent pom.xml to include new module

Code Quality Improvements

• Fixed unsafe Optional.get() calls in Basic.java with orElseThrow()
• Fixed unsafe Optional.get() calls in OutputSchema.java with proper error handling
• Fixed unsafe Optional.get() calls in RequestConfirmationLlmRequestProcessor.java
• Added meaningful error messages for IllegalStateException cases
• Removed duplicate condition check in RequestConfirmationLlmRequestProcessor
• Removed unused logger imports from InstructionUtils.java

Testing
Unit Tests
Added CodeAssistantTest.java with 10 unit tests covering:

• generateCode functionality (2 tests)
• reviewCode functionality (2 tests)
• explainCode functionality (2 tests)
• debugCode functionality (2 tests)
• ROOT_AGENT validation (2 tests)
  All 10 unit tests pass successfully
  All 24 modules pass successfully (BUILD SUCCESS)
  ./mvnw test completed with no failures

Manual E2E Tests
Tested code assistant tutorial with GOOGLE_API_KEY
Verified all 4 tools work correctly via web interface at http://localhost:8080
Tested existing tutorials still work after changes

[google-cla]

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[Rajkumar7633]

No existing issue. This PR adds:

1. New code assistant tutorial feature

2. Critical code quality improvements (unsafe Optional.get() fixes)
   Problem:

3. Missing code assistant tutorial for developers

4. Unsafe Optional.get() calls that could cause NoSuchElementException crashes

5. Inconsistent error handling in LLM flow processing
   Solution:

6. Added new code-assistant tutorial with 4 tools (generate, review, explain, debug code)

7. Replaced unsafe .get() calls with orElseThrow() for better error handling

8. Added meaningful error messages for debugging

9. Removed duplicate condition checks
   Testing Plan:

Unit Tests:

• All 24 modules pass successfully (BUILD SUCCESS)
• ./mvnw test completed in 2:23 min with no failures

Manual E2E Tests:

• Tested code assistant tutorial with GOOGLE_API_KEY
• Verified all 4 tools work correctly via web interface
• Tested existing tutorials still work after changes

[hemasekhar-p]

Hi @Rajkumar7633, thank you for your contribution! We appreciate you taking the time to submit this pull request. To proceed with the review, could you please address the following,

1. Please provide clear and detailed description of your PR.
2. Please include corresponding unit tests to verify your changes.
3. As per our contribution policy, please squash your changes into a single commit.

[hemasekhar-p]

@Rajkumar7633, thank you for addressing the feedback and squashing your commits, Currently this PR is under review by our team, we will keep you posted if any additional information is required. thank you