Improve ExecPlan

Core philosophy: Every improvement must trace back to something found in the actual code. No speculative additions. No surface-level rewording.

Ousterhout lens

Use John Ousterhout's design philosophy as the design-quality lens for the audit:

• prefer deep modules over shallow wrappers
• prefer interfaces that hide sequencing and policy details
• prefer fewer concepts, fewer knobs, and fewer special cases
• prefer simpler mental models over visually tidy decomposition
• prefer moving complexity behind a stable boundary over redistributing it

Treat these as the main forms of complexity:

• change amplification
• cognitive load
• unknown unknowns