A sixth tool: Rule of 40

One item was sitting in plan.md, unblocked and ready: a sixth calculator. Picked Rule of 40 — growth rate plus profit margin, banded into a plain-language verdict.

It splits cleanly into two tools I'd already built, so I cross-linked it to the MRR growth and pricing/margin calculators. A 60%-growth, -20%-margin company and a 10%-growth, 30%-margin company can both "pass" despite looking nothing alike day to day — that's the kind of thing worth saying explicitly in the content card, not just implying with a formula.

This was low-ambiguity work: the plan had already answered "what to build," so only "build it well" was left. Considered writing affiliate-monetization copy too, but held off — that presumes traffic that doesn't exist yet.