♻️ Merge message context into raw logs event at collection time

[BenoitZugmeyer]

Motivation

This is a small refactor that will simplify #4920

Logs collection carried the user-provided message context as a separate messageContext field through the lifecycle, only to merge it into the event during assembly. This indirection added complexity to the data flow for no benefit, since the context is always meant to end up on the log event itself.

Changes

• Merge messageContext directly into rawLogsEvent at collection time (console, logger, and runtime error sources) using combine, preserving the existing precedence (message context overrides base event fields).
• Remove the messageContext field from RawLogsEventCollectedData.
• Add an index signature to CommonRawLogsEvent so user context fields are accepted by the type system.
• Update affected specs and add a test asserting message context precedence over native raw log fields.

Test instructions

• In the sandbox, send a log with extra context (e.g. DD_LOGS.logger.log('hello', { foo: 'bar' })) and confirm the context fields appear on the sent log event.
• Verify that passing a context key that collides with a native field (e.g. message) overrides the native value in the sent event.

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Updated documentation and/or relevant AGENTS.md file

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	182.00 KiB	182.00 KiB	0 B	0.00%	✅
Rum Profiler	8.43 KiB	8.43 KiB	0 B	0.00%	✅
Rum Recorder	25.32 KiB	25.32 KiB	0 B	0.00%	✅
Logs	57.93 KiB	57.88 KiB	-52 B	-0.09%	✅
Rum Salesforce	N/A	140.05 KiB	N/A	N/A	N/A
Rum Slim	140.05 KiB	140.05 KiB	0 B	0.00%	✅
Worker	22.96 KiB	22.96 KiB	0 B	0.00%	✅
Rum Shopify	N/A	206.79 KiB	N/A	N/A	N/A
Rum-shopify Profiler	N/A	8.43 KiB	N/A	N/A	N/A
Rum-shopify Recorder	N/A	3.74 KiB	N/A	N/A	N/A

[datadog-prod-us1-5]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 77.01% (+0.00%)

_{This comment will be updated automatically if new data arrives.
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[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-04T08:09:27.033904Z	fdfea55	Draft marked ready

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