fix(producer,cli): round the fallback dB consistently, thread the verify threshold through

Review feedback on #2411 (Rames): the crash-survival RenderCaptureObservability
mirror passed deFallbackFailedDb raw/unrounded while the render_complete
perfSummary path rounded to 1 decimal — the same underlying PSNR could ship two
different values to PostHog depending on which event fired. Extracted the
existing inline round/clamp expression (previously duplicated for verifyMinDb
and fallbackFailedDb) into a shared roundDb helper, applied once at the single
point deFallbackFailedDb is derived from the thrown error so both downstream
consumers agree.

Also threads verifyThresholdDb (captured on the error but never propagated,
per the nit) through DrawElementPerfInput/RenderCaptureObservability/render.ts/
telemetry as de_fallback_threshold_db on both events — the HF_DE_VERIFY_MIN_DB
value the failing dB breached, letting ops read "28.4dB failed a 32dB
threshold" directly instead of cross-referencing config.

packages/cli/src/commands/render.ts

@@ -2066,6 +2066,7 @@ function trackRenderMetrics(
     deFallbackReason: perf?.drawElement?.fallbackReason,
     deFallbackFailedDb: perf?.drawElement?.fallbackFailedDb,
     deFallbackFrameIndex: perf?.drawElement?.fallbackFrameIndex,
+    deFallbackThresholdDb: perf?.drawElement?.fallbackThresholdDb,
     deBlankSuspects: perf?.drawElement?.blankSuspects,
     deBlankDeterministicAccepts: perf?.drawElement?.blankDeterministicAccepts,
     deBlankRecaptures: perf?.drawElement?.blankRecaptures,