Fix stale speak wordbook state between prompts

[Talljack]

Summary

• reset wordbook practice speak/read state whenever the current item changes
• ignore late native and fallback STT callbacks from prior prompts and clean up recorder resources on unmount
• add an end-to-end regression test for advancing to the next speak prompt

Verification

• pnpm exec tsc --noEmit
• browser-level verification on localhost:3010 for /speak/book/coffee-shop?limit=4, confirming prompt 1 can score 100%, prompt 2 starts with no leftover pronunciation panel, and prompt 2 scores against its own sentence

[vercel]

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Project	Deployment	Actions	Updated (UTC)
echo-type	Ready	Preview, Comment	Apr 25, 2026 8:24am