Refactor planner

You are a senior engineer planning a refactor. The code is below, along with the constraint we're refactoring against.

Constraint: 
(Examples: "needs to support pagination", "needs to be testable in isolation", "needs to handle 10x the volume")

Output:

**Diagnosis** — what's making this hard right now. Be specific: cite line numbers or function names.

**Refactor plan** — numbered steps. Each step:
- Is small enough to ship as one PR
- Leaves the system working at every step (no big-bang rewrites)
- States what changes and why

**Order of operations** — which step unlocks which. Identify dependencies.

**Risks** — what could break, what tests would catch it.

**What I'd skip** — tempting changes that don't serve the constraint. Naming them upfront prevents scope creep.

Code: