feat: add semantic memory storage foundation

[Dhirenderchoudhary]

Description

Adds the step-one foundation for Continuous Semantic Memory: a repo-scoped local memory manager with JSON persistence, add/list/delete/clear operations, and simple relevance lookup. This PR does not add commands, prompt injection, SQLite/vector search, or UI changes.

Phase 1: #619

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Testing

Automated Tests

• New features include passing tests in .spec.ts/tsx files
• All existing tests pass (pnpm test:all completes successfully)
• Tests cover both success and error scenarios

Manual Testing

• Tested with Ollama
• Tested with OpenRouter
• Tested with OpenAI-compatible API
• Tested MCP integration (if applicable)

Checklist

• Code follows project style guidelines
• Self-review completed
• Documentation updated (if needed)
• No breaking changes (or clearly documented)
• Appropriate logging added using structured logging (see CONTRIBUTING.md)

[akramcodez]

Hey @Dhirenderchoudhary! Thanks again for working on this. I just updated the implementation plan based on the architecture discussion and created a dedicated feat/semantic-memory branch for this feature. Could you please retarget this PR to the feat/semantic-memory branch instead of main? Thanks!

[Dhirenderchoudhary]

@AkramCode I'll retarget the PR and look into the updated flow.

There are a few test failures in the CI/CD that I've already fixed in this PR. Should I keep those fixes in this PR, or would you prefer that I move them to a separate PR?