fix(client): keep v-click hidden state on annotated code and KaTeX blocks

[lazerg]

A fenced code block with a line-highlight annotation (```ts {*}) placed inside <v-click> was already visible on the slide's first render, while the rest of the <v-click> content stayed hidden. Navigating one click forward and back fixed it.

CodeBlockWrapper gets the v-click directive applied to its root element, and the directive's effect adds slidev-vclick-hidden there. The wrapper's own effect then calls classList.toggle(CLASS_VCLICK_HIDDEN, hide) for its ranges, and for any normal range (*, 1-3, …) that removes the class the directive just added. On mount the wrapper's effect runs last, so the block ends up visible; on later click changes the directive wins, which is why navigating repairs it.

The wrapper now only touches the class when its own hide range put it there, so a click directive on the same element keeps ownership. CLASS_VCLICK_HIDDEN_EXP isn't usable for this, since v-click only sets it on the .hide path. KaTexBlockWrapper had the same code and gets the same fix.

Added a Cypress case (page 17 of the basic fixture) that asserts the wrapper is hidden on first render and revealed after one click. It fails on main and passes here. Also checked a {hide|1|2} deck by hand to confirm the hide range still hides and reveals as before.

Fixes #2711

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commit: b07c689