fix(react-doctor): detect index-derived key locals

[JW-Rami]

What

Detect no-array-index-as-key when a JSX key references a local constant whose initializer is derived from the .map() index parameter.

Why

The rule already caught inline template literals such as key={${item.id}-${index}}, but the same expression could be hoisted into const itemKey = ... and then used as key={itemKey} without a diagnostic.

How to test

• nr test
• nr lint
• nr typecheck
• nr format

---

Note

Medium Risk
Expands the no-array-index-as-key rule to follow simple local variable initializers inside .map() callbacks, which can introduce new diagnostics (potentially false positives/negatives) in existing codebases.

Overview
Improves no-array-index-as-key to also flag key={itemKey} patterns where itemKey is a local variable derived from a .map() index parameter (including custom index parameter names).

The rule now locates the enclosing .map() callback, tracks its index parameter, and (when the key expression is an identifier) inspects top-level variable initializers in that callback while stopping at nested function boundaries to avoid accidental cross-scope resolution.

Adds regression tests covering index-derived locals, stable-field-only locals, and nested function shadowing.

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