feat: add backend orchestration core and local skill assets

[chiraghontec]

Summary

This PR adds backend orchestration core behavior for chat handling and approval gating, plus skill assets and lock metadata required for the local agent workflow.

What is included

• Backend orchestration updates across retrieval, reasoning, execution, controller, memory, and chat route wiring
• Backend test and pytest configuration additions
• Skill packages added under the local agent skills directory
• Skills lock file added for reproducible skill state

Validation

• Backend tests passing on this branch: 3 passed

Notes

• Core repository hygiene and frontend lockfile were intentionally split and already merged to main in a separate commit.

Risks

• This change set is broad and includes both backend runtime logic and skill content assets.
• Follow-up PRs can further split skill content from runtime code if needed for easier review.

Reviewer checklist

• Verify backend orchestration flow and approval behavior
• Verify chat endpoint response shape and trace behavior
• Verify skill content and lock alignment
• Confirm test suite passes locally