fix(dart): Add span v2 envelope metadata

[buenaflor]

📜 Description

Add the span v2 envelope item container metadata required by Relay for pre-encoded span batches.

Span v2 envelope item payloads now include version: 2 and ingest_settings with automatic IP and user-agent inference, while logs and metrics continue to use the plain items container.

💡 Motivation and Context

Fixes #3690.

The span v2 envelope item payload contract requires top-level version and ingest_settings fields in addition to the items array. Without these fields, span v2 batches do not fully match the expected ingest payload shape.

💚 How did you test it?

• fvm dart format lib/src/sentry_envelope.dart test/sentry_envelope_test.dart
• fvm dart analyze lib/src/sentry_envelope.dart test/sentry_envelope_test.dart
• fvm dart test test/sentry_envelope_test.dart
• Pre-commit hooks ran staged Dart formatting and package analyze successfully.

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes
• No new PII added or SDK only sends newly added PII if sendDefaultPii is enabled
• I updated the docs if needed
• All tests passing
• No breaking changes

🔮 Next steps

Made with Cursor

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

📋 Changelog Preview

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Entries from this PR are highlighted with a left border (blockquote style).

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Fixes

• (dart) Add span v2 envelope metadata by buenaflor in #3700

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_{🤖 This preview updates automatically when you update the PR.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.85%. Comparing base (87fcdd8) to head (1f3cd4a).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3700      +/-   ##
==========================================
- Coverage   86.96%   86.85%   -0.12%     
==========================================
  Files         335      335              
  Lines       11976    11988      +12     
==========================================
- Hits        10415    10412       -3     
- Misses       1561     1576      +15     

Flag	Coverage Δ
sentry	86.76% <100.00%> (-0.01%)	⬇️
sentry_dio	97.73% <ø> (ø)
sentry_drift	93.57% <ø> (ø)
sentry_file	65.29% <ø> (ø)
sentry_firebase_remote_config	100.00% <ø> (ø)
sentry_flutter	91.15% <ø> (-0.38%)	⬇️
sentry_hive	77.48% <ø> (ø)
sentry_isar	74.37% <ø> (ø)
sentry_link	21.50% <ø> (ø)
sentry_logging	97.01% <ø> (ø)
sentry_sqflite	88.81% <ø> (ø)
sentry_supabase	97.27% <ø> (ø)

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☔ View full report in Codecov by Sentry.
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[github-actions]

iOS Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1259.40 ms	1261.11 ms	1.72 ms
Size	5.73 MiB	6.18 MiB	463.86 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
1adf565	1264.51 ms	1265.22 ms	0.71 ms
d789735	1240.58 ms	1246.41 ms	5.82 ms
2f63d89	1251.67 ms	1263.94 ms	12.27 ms
cdf371b	1246.24 ms	1251.10 ms	4.86 ms
fd88186	1255.06 ms	1252.76 ms	-2.30 ms
ce5c42b	1246.06 ms	1251.91 ms	5.85 ms
e5ae2a6	1240.48 ms	1253.26 ms	12.78 ms
944b773	1252.82 ms	1254.08 ms	1.27 ms
73dca78	1246.65 ms	1265.42 ms	18.76 ms
7cfbbd6	1270.63 ms	1285.36 ms	14.72 ms

App size

Revision	Plain	With Sentry	Diff
1adf565	5.66 MiB	6.10 MiB	451.33 KiB
d789735	5.53 MiB	5.96 MiB	443.28 KiB
2f63d89	5.65 MiB	6.09 MiB	446.25 KiB
cdf371b	5.53 MiB	6.02 MiB	501.23 KiB
fd88186	5.53 MiB	6.00 MiB	479.94 KiB
ce5c42b	5.73 MiB	6.17 MiB	455.86 KiB
e5ae2a6	5.65 MiB	6.09 MiB	446.96 KiB
944b773	5.53 MiB	6.00 MiB	479.98 KiB
73dca78	7.86 MiB	9.44 MiB	1.58 MiB
7cfbbd6	7.86 MiB	9.44 MiB	1.58 MiB

[github-actions]

Android Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	374.18 ms	352.76 ms	-21.42 ms
Size	14.31 MiB	15.56 MiB	1.25 MiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
bfabaf2	408.04 ms	444.38 ms	36.34 ms
fec56a1	370.66 ms	369.28 ms	-1.38 ms
8541716	437.14 ms	443.65 ms	6.51 ms
0fb45d0	482.79 ms	554.02 ms	71.23 ms
0fb3800	465.64 ms	536.77 ms	71.13 ms
e04b24b	504.72 ms	516.43 ms	11.71 ms
944b773	470.54 ms	480.18 ms	9.64 ms
cdf371b	367.64 ms	377.02 ms	9.38 ms
0bea8d9	389.45 ms	394.96 ms	5.50 ms
5b9a0da	446.94 ms	449.22 ms	2.28 ms

App size

Revision	Plain	With Sentry	Diff
bfabaf2	13.93 MiB	15.06 MiB	1.13 MiB
fec56a1	14.31 MiB	15.49 MiB	1.19 MiB
8541716	13.93 MiB	15.00 MiB	1.06 MiB
0fb45d0	6.54 MiB	7.70 MiB	1.17 MiB
0fb3800	6.54 MiB	7.69 MiB	1.15 MiB
e04b24b	13.93 MiB	15.00 MiB	1.06 MiB
944b773	13.93 MiB	15.00 MiB	1.06 MiB
cdf371b	13.93 MiB	15.18 MiB	1.25 MiB
0bea8d9	14.31 MiB	15.56 MiB	1.25 MiB
5b9a0da	13.93 MiB	14.93 MiB	1.00 MiB