Fix silent playback: revert useSPN -> worklet, match sample rate

Read the @csound/browser source: useSPN uses createScriptProcessor(0,...) (a deprecated node that was producing silence here) and CLOSES a provided AudioContext on teardown.

• Drop useSPN; let Csound use the worklet with our provided, resumed context.

• Create the AudioContext at sampleRate 44100 to match the CSD (was 48k default).

• Recreate the context if it ever ends up closed.

Verified: objectively with Puppeteer by splicing an AnalyserNode before the destination and reading levels: maxRMS 0.33 (was silent). ctx state "running".

▶ Play it: Ballroom Leviathan — a horn-and-piano genre that plays almost entirely sampled instruments https://stellate.app/?genre=bigband&seed=4237&path=814.14134,833.14167,795.14167&xdur=13.122

e14a6d4 https://github.com/aboard-io/stellate/commit/e14a6d4534fbe2fb9d5c84bb20a1b3a53e2411ff