fix(plugin): correct argtype inference so URL param args apply to all controls

[Burzmalian]

Summary

Fixes three bugs in packages/plugin/src/docs/infer-type.ts and custom-elements.ts that caused Storybook URL ?args= parameters to be silently dropped for Stencil components.

Root causes

1. inferSBType: in operator used on an array (infer-type.ts)

prop.type.toLowerCase() in scalarTypes checks object keys, not array elements — always false. Every scalar prop (string, number, boolean) got type { name: 'other' } instead of the correct scalar type, preventing Storybook from coercing URL arg values.

2. mapPropOptions: plain-type props mapped to [undefined] (infer-type.ts)

Stencil emits values: [{ type: "string" }] (no value key) for non-union props. The old filter kept these entries and .map(({ value }) => value) produced [undefined]. Since [undefined].length > 0, the original patch's length > 0 guard didn't help — Storybook saw options: [undefined] and rejected any URL arg value.

3. inferSBType: union/enum types returned { name: 'other' } (infer-type.ts)

Storybook's internal mapArgsToTypes passes each arg through a map() function that returns INCOMPATIBLE for type.name === 'other' (unless type.value === 'ReactNode'). This caused all radio/select union-typed props to be dropped when set via URL args. Fixed by returning { name: 'enum', value: [...] } when enumerated values are present — matching the type Storybook expects for these controls.

4. tests/hmr.e2e.ts — fix flaky iframe switching

Replaced the inline switchFrame predicate (which raced against Storybook's load cycle) with a dedicated switchToPreviewIframe() helper that waits for #storybook-preview-iframe to exist and for data-is-loaded=true before switching frame context. Eliminates intermittent frame-not-found failures in CI.

Changes

• infer-type.ts — Array.includes() replaces in for scalar type check
• infer-type.ts — mapPropOptions filters out entries with no value key
• infer-type.ts — inferSBType returns SBEnumType for union types with enumerated values
• custom-elements.ts — options: undefined instead of options: [] for props with no enumerated values
• .gitignore — add .pnpm-store/
• tests/hmr.e2e.ts — replace racy switchFrame predicate with switchToPreviewIframe() helper

Testing

Verified manually against the example package with all Stencil prop types (string, number, boolean, union/radio, union/select). URL args now apply correctly for all scalar and enum-typed props.

/iframe.html?id=mycomponent--primary&args=first:Gyles;radioTest:baz