Memory Sync Error Classification Improvements

The HTTP error handler for memory operations now parses the server error body and maps specific server error messages to typed error codes:

• "memory store has reached its memory limit" → store_full
• "content must be at most 102400 bytes" → content_too_large
• "memory content appears to contain a credential or API key" → content_secret
• Path validation failures ("path must be at most 1024 bytes", "path must be NFC-normalized", etc.) → invalid_path
• "cannot modify archived resource" → store_archived

Users will see more specific notifications when memory writes fail for these reasons, rather than generic HTTP error messages.