Strengthen daterange integration test with compliant test stream

[devin-ai-integration]

Summary

The previous daterange test stream contained an EXT-X-DATERANGE update tag without START-DATE, which Android and Web parsers reject — leaving duration/endDate null and endTime infinite on those platforms, so the test couldn't assert finite metadata or cue lifecycle events.

Switch daterange_test.dart (and the example app's "Daterange source" button) to the new spec-compliant daterange-test.m3u8 stream and strengthen assertions on the first cue (test-010, active 10s–15s into playback):

• exact id, cueClass, startDate, endDate, duration (5s), plannedDuration
• finite endTime with endTime - startTime ≈ 5
• non-empty scte35Out/scte35In payloads and forwarded X-COM-* custom attributes
• ENTERCUE and EXITCUE events fire as playback crosses the range (new _pumpUntil polling helper instead of a fixed 10s wait)

Link to Devin session: https://dolby.devinenterprise.com/sessions/9c8aebec43564a36a78d52fa710c8fe5
Open in Devin Desktop: https://dolby.devinenterprise.com/desktop/session/9c8aebec43564a36a78d52fa710c8fe5?variant=devin

[devin-ai-integration]

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[devin-ai-integration]

Tested the daterange web support end-to-end on Chrome (Devin session)

Web integration suite (flutter drive + chromedriver 152, CI-mirrored command): ✅ All tests passed, including both daterange cue tests (all metadata assertions for test-010) and the no-hlsDateRange negative test. Note: before commit 3daedcd (daterange track forced from disabled → hidden on web) the ENTERCUE/EXITCUE assertions failed — the fix is required.

Example app on Chrome — clicked "Daterange source", console output:

Daterange track added: 6
DateRangeCue added: id=test-010, startDate=2015-07-30 05:36:43.000, endDate=2015-07-30 05:36:48.000, duration=5, class=com.theoplayer.daterange-test, customAttributes={X-COM-THEOPLAYER-TEST-LABEL: cue-010, X-COM-THEOPLAYER-TEST-INDEX: 1.0}
ENTERCUE: id=test-010 at startTime=10
EXITCUE: id=test-010 at endTime=15
ENTERCUE: id=test-020 at startTime=20
EXITCUE: id=test-020 at endTime=25

ADDCUE/ENTERCUE/EXITCUE all fire on web with finite endDate/endTime and duration=5 — the discrepancy seen with the old malformed stream is resolved.

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