Default debugger version and embed build identity in snapshots

[watson]

Motivation

The Browser Debugger SDK should be able to pick up the browser build version injected by the Live Debugger build plugin so applications do not need to pass the same deployed build identifier into datadogDebugger.init() a second time.

The debugger snapshot payload also needs applicationId and version so downstream browser-build and source-resolution flows can identify the correct browser build when git tags are unavailable.

Changes

Version defaulting from build metadata

• default datadogDebugger.init().version from the build-plugin metadata when callers omit version
• keep an explicit init({ version }) value authoritative and warn if it disagrees with the injected build-plugin version
• document that version is optional, but browser build lookup and source-aware resolution depend on an immutable deployed build identifier when available

Snapshot build identity

• include applicationId and version as a structured build object inside the debugger.snapshot payload (debugger.snapshot.build = { applicationId, version })
• this replaces the earlier approach of putting application_id as a top-level field and duplicating application_id/version into ddtags, which was vulnerable to tag collision from downstream enrichment
• the build object rides on the existing @debugger.snapshot column projection, so the web UI reads it without any query changes

Version documentation

• document that version is optional in the Browser Debugger README and API docs
• clarify that when provided, version should be the immutable deployed browser build identifier
• clarify graceful degradation when version is absent

Test instructions

Run:

yarn test:unit --spec packages/debugger/src/entries/main.spec.ts
yarn test:unit --spec packages/debugger/src/domain/api.spec.ts

Part of larger effort

This PR is one part of the browser Live Debugger source-resolution work across multiple repositories:

• https://github.com/DataDog/dd-source/pull/415107
• https://github.com/DataDog/dd-source/pull/418329
• https://github.com/DataDog/debugger-backend/pull/2053
• https://github.com/DataDog/web-ui/pull/298258
• Validate optional live-debugger version build-plugins#325
• Source build version from shared metadata.version build-plugins#326

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

[watson]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Default debugger version and embed build identity in snapshots #4511 👈 (View in Graphite)
• Default args and locals params in debugger snapshot hooks #4609
• Switch debugger delivery to public ClientTokenAuth endpoint #4480
• Add Live Debugger package #4449 : 4 other dependent PRs (#4503 , #4508 , #4509 and 1 other)
• Fix TanStack Router lint resolution in test app #4513
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	169.51 KiB	169.51 KiB	0 B	0.00%	✅
Rum Profiler	5.97 KiB	5.97 KiB	0 B	0.00%	✅
Rum Recorder	21.23 KiB	21.23 KiB	0 B	0.00%	✅
Logs	54.70 KiB	54.70 KiB	0 B	0.00%	✅
Rum Slim	127.85 KiB	127.85 KiB	0 B	0.00%	✅
Worker	22.99 KiB	22.99 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base CPU Time (ms)	Local CPU Time (ms)	𝚫%
RUM - add global context	0.0019	0.0026	+36.84%
RUM - add action	0.0095	0.015	+57.89%
RUM - add error	0.0101	0.0124	+22.77%
RUM - add timing	0.0005	0.0007	+40.00%
RUM - start view	0.012	0.0116	-3.33%
RUM - start/stop session replay recording	0.0007	0.001	+42.86%
Logs - log message	0.0194	0.0193	-0.52%

🧠 Memory Performance

Action Name	Base Memory Consumption	Local Memory Consumption	𝚫
RUM - add global context	38.61 KiB	38.24 KiB	-374 B
RUM - add action	64.97 KiB	64.34 KiB	-646 B
RUM - add timing	37.33 KiB	38.78 KiB	+1.45 KiB
RUM - add error	69.54 KiB	68.40 KiB	-1.14 KiB
RUM - start/stop session replay recording	42.58 KiB	41.23 KiB	-1.35 KiB
RUM - start view	483.21 KiB	483.70 KiB	+505 B
Logs - log message	54.48 KiB	54.64 KiB	+157 B

🔗 RealWorld

[datadog-prod-us1-4]

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 84.62%
• Overall Coverage: 77.05% (+0.09%)

_{This comment will be updated automatically if new data arrives.
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