[Feature] Evolve AssetAgent into a full ISA

[eraflo]

With the foundational asset loading systems in place (from #174), this issue focuses on elevating the AssetAgent to a true Intelligent Subsystem Agent (ISA) as envisioned by the SAA.

This includes three key responsibilities:

1. Metrics Collection: The agent must track and report key performance indicators (KPIs), such as total memory usage of loaded assets (system RAM and VRAM) and disk I/O bandwidth. These will be fed into the khora-telemetry service.
2. Strategy Definition: The agent will expose a set of distinct operational strategies (e.g., HighQuality, LowMemory).
3. Contract Implementation: The agent will implement the basic ISA trait, allowing the future DCC to query its status, list available strategies, and command a strategy switch.

The goal is to demonstrate that the AssetAgent is reporting its resource usage and that its behavior can be manually changed by switching its strategy, causing it to request different asset variants from the VFS.