fix: install @google/generative-ai and use writeFile for atomic writes in ConflictResolver

[Copilot]

Description

Two correctness fixes: ensures the @google/generative-ai package is fully installed so AIService.ts can resolve its import, and replaces a potentially partial write() call in ConflictResolver with writeFile() to guarantee full-buffer writes before fsync+rename.

Dependency resolution

• @google/generative-ai was already declared in package.json and package-lock.json but absent from node_modules; ran npm install to populate it, unblocking TypeScript compilation.

Atomic write correctness in ConflictResolver.applyResolution

• FileHandle.write(buffer, 0, buffer.length) does not guarantee all bytes are written in a single call — a short write silently truncates the resolved file before rename() completes.
• Replaced with FileHandle.writeFile(buffer), which loops internally until the entire buffer is flushed, preserving the atomic-replace guarantee.

// Before — susceptible to short writes
await tempHandle.write(buffer, 0, buffer.length);

// After — full buffer guaranteed before fsync + rename
await tempHandle.writeFile(buffer);

Related Issue

Closes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 📝 Documentation update
• 🔧 Refactor / internal improvement
• 🤖 CI/CD or tooling change
• ⬆️ Dependency update

Checklist

• I have read the CONTRIBUTING guidelines (if present)
• My code follows the existing code style
• I have added or updated tests that cover my changes
• All existing tests pass locally
• I have updated the documentation where necessary
• My changes do not introduce new security vulnerabilities

How Has This Been Tested?

npm run lint (tsc --noEmit) passes with zero errors after installing the dependency. CodeQL analysis returned 0 alerts.

Screenshots (if applicable)

N/A

Additional Notes

node_modules/ remains gitignored; only package-lock.json changes (if any) are committed.

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