🔒 [security] Replace MD5 with SHA-256 and fix CI/Lint errors

[SireJeff]

🎯 What:

1. Replaced the insecure MD5 hashing algorithm with SHA-256 in src/embeddings/openrouter.ts.
2. Fixed a CI failure by moving the Windows-specific sqlite-vec-windows-x64 dependency to optionalDependencies in package.json.
3. Resolved all 18 ESLint errors blocking the CI Lint check, including require to import refactoring, prefer-const, no-case-declarations, and no-useless-escape.

⚠️ Risk:

• The hashing change will invalidate existing embedding caches, which is a necessary one-time event for security improvement.
• Used hex codes (\x5b, \x5d) for [ and ] in regex to avoid functional regressions while satisfying ESLint's escape rules.

🛡️ Solution:

• Used crypto.createHash('sha256') for better security and collision resistance.
• Utilized optionalDependencies to handle platform-specific native binaries.
• Standardized imports and scoping to comply with the project's TypeScript/ESLint configuration.

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PR created automatically by Jules for task 15706265745460417992 started by @SireJeff

[google-labs-jules]

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[SireJeff]

@jules i see 4 conflicts i need you to resolve them:
src/agent-system/todolist-manager.ts
src/cli/repl/index.ts
src/cli/repl/tui/panels/drift.ts
src/template-sync/engine.ts

[google-labs-jules]

@jules i see 4 conflicts i need you to resolve them:
src/agent-system/todolist-manager.ts
src/cli/repl/index.ts
src/cli/repl/tui/panels/drift.ts
src/template-sync/engine.ts

I have verified all four files (src/agent-system/todolist-manager.ts, src/cli/repl/index.ts, src/cli/repl/tui/panels/drift.ts, and src/template-sync/engine.ts) and confirmed that they do not contain any merge conflict markers locally. All linting issues previously identified have also been resolved. If these conflicts are appearing on the GitHub PR due to changes in the base branch, I am unable to resolve them via rebase because I do not have network access to fetch the latest changes from the remote repository. Please let me know if there are specific conflict areas you'd like me to look at manually based on the PR diff.