Rebuild free trial and KDP royalty calculators for most users

[RaviTejaKNTS]

What changes

• Free trial conversion calculator, rebuilt. Basic asks for trial type, starts, and paid, and opens on an example. Advanced holds the follow-up window, activation, pricing, a target, and up to 12 cohorts. The result leads with the rate and a grid of 100, then where the rate sits, then the supporting numbers as a list. New page content.
• KDP royalty calculator, rebuilt. Format, price, interior, and page count in Basic, with deeper options in Advanced. New page content.
• Shared UI. Tool workbench, more ECharts types, UiMetricGroup layout="list", a vertical UiRangeMarker legend, funnel labels beside the shape, and * on required fields. Components gallery examples.
• Shared KDP engine fix. Print rounding now matches KDP's calculator, and eBook delivery half cents round correctly. This also corrects the KDP minimum list price and price profit calculators.
• Docs and skills. Short tool skills, one Opus session per tool for plan, interface, and writing, integration in its own session, a friendly direct writing voice, and one tool at a time by default.

Checks

• npm run quality: 79 of 79 pass.
• Sol audits passed for both tools. Sol review of the shared UI passed, and the last round passed on round 2.
• Desktop and mobile checks with valid, invalid, and extreme values.

After merge

Production data through the tools publisher: tool versions (free trial 1.1.0, KDP royalty 1.2.0, minimum list price 1.0.1, price profit 1.0.2), new search descriptions for both rebuilt tools, and a new free trial card description. Already applied and verified in development.

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