Premium Analytics: add Stats streak endpoint

[kangzj]

Fixes #

Proposed changes

• Add Premium Analytics data package support for the Stats streak endpoint, following the Stats endpoint patterns established in Premium Analytics: add Stats endpoint foundation #49886.
• Wire the endpoint-specific query, hook, public exports, and sanitizer/normalizer registration where applicable.
• Normalize raw timestamp-count streak payloads into date-keyed post counts aligned with Calypso's posting activity parsing.
• Keep endpoint typing tied to sanitizer keys, with focused fixtures/tests for the raw endpoint payload shape.

Related product discussion/links

• Builds on Premium Analytics: add Stats endpoint foundation #49886.

Does this pull request change what data or activity we track or use?

No. This only adds typed client data/query integration for an existing Stats API endpoint.

Testing instructions

• pnpm --dir projects/packages/premium-analytics test -- packages/data/src/queries/tests/stats-queries.test.ts packages/data/src/hooks/tests/stats-exports.test.ts packages/data/src/processing/stats/tests/streak.test.ts --runInBand
• pnpm exec eslint --max-warnings=0
• pnpm --dir projects/packages/premium-analytics run typecheck
• git diff --check

[jp-launch-control]

Code Coverage Summary

This PR did not change code coverage!

That could be good or bad, depending on the situation. Everything covered before, and still is? Great! Nothing was covered before? Not so great. 🤷

Full summary · PHP report

[github-actions]

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[kangzj]

Review-cycle audit complete: no actionable reviewer comments remain. The PR is ready for team review; GitHub reports no required checks for this branch, and the visible CI list is passing except the non-required coverage summary pending because parent coverage is unavailable.

Local verification: jp test js packages/premium-analytics skipped because this project has no test-js Composer script; jp build packages/premium-analytics completed the package build phases, then the local container failed on an ignored generated boot-asset file permission (EACCES). No source changes or push were made.