👷 replace lerna publish with yarn npm publish

[BenoitZugmeyer]

This is a follow-up of #4275

Motivation

Second step toward removing lerna from the project. This PR replaces lerna publish with
yarn workspaces foreach npm publish, and switches package file inclusion from .npmignore
to the files field in package.json for reliable yarn-compatible packaging.

Changes

The publish script now uses yarn workspaces foreach npm publish with YARN_NPM_AUTH_TOKEN
for authentication, and gains a --dry-run option. The old lerna-based script is preserved
as publish-npm-legacy.ts as a fallback. The check-packages.ts script is updated to use
yarn pack for dry-run validation, and now also verifies that packed files match the files
field. All public packages gain a files field (replacing .npmignore) and a LICENSE
symlink so the license is included in published tarballs.

Test instructions

• Run node scripts/deploy/publish-npm.ts --dry-run — should list files that would be published without actually publishing
• Run node scripts/check-packages.ts — should pass without errors

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	175.00 KiB	175.00 KiB	0 B	0.00%	✅
Rum Profiler	6.16 KiB	6.16 KiB	0 B	0.00%	✅
Rum Recorder	27.46 KiB	27.46 KiB	0 B	0.00%	✅
Logs	56.80 KiB	56.80 KiB	0 B	0.00%	✅
Flagging	944 B	944 B	0 B	0.00%	✅
Rum Slim	130.64 KiB	130.64 KiB	0 B	0.00%	✅
Worker	23.63 KiB	23.63 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base CPU Time (ms)	Local CPU Time (ms)	𝚫%
RUM - add global context	0.0046	0.0061	+32.61%
RUM - add action	0.0127	0.0173	+36.22%
RUM - add error	0.0135	0.0147	+8.89%
RUM - add timing	0.0025	0.0033	+32.00%
RUM - start view	0.0122	0.0157	+28.69%
RUM - start/stop session replay recording	0.0007	0.0008	+14.29%
Logs - log message	0.0144	0.0202	+40.28%

🧠 Memory Performance

Action Name	Base Memory Consumption	Local Memory Consumption	𝚫
RUM - add global context	27.37 KiB	26.68 KiB	-705 B
RUM - add action	53.07 KiB	52.15 KiB	-942 B
RUM - add timing	25.97 KiB	26.33 KiB	+373 B
RUM - add error	55.69 KiB	55.25 KiB	-450 B
RUM - start/stop session replay recording	25.52 KiB	25.39 KiB	-136 B
RUM - start view	462.52 KiB	461.86 KiB	-679 B
Logs - log message	44.79 KiB	44.56 KiB	-237 B

🔗 RealWorld

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 77.21% (+0.00%)

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