CMM-2141: Fix subscriber email stats missing for recent posts

[adalpari]

Description

Subscriber Stats → Subscribers → Emails did not list recently published/emailed
posts in the app, while the web (Calypso / WP Admin) showed them correctly. The issue was
persistent, survived force-stop / cache-clear / pull-to-refresh, and self-resolved after
~1 week — at which point the post reappeared.

Root cause: the app requested the stats/emails/summary endpoint with parameters that
don't match the web, so a freshly emailed post (few/zero opens) was never in the returned
result set:

• Classic stats (fluxc) — sent sort_field=POST_ID (the enum's toString(), an
  invalid value the server ignores) and no period, so results came back sorted by the
  server default (opens). Fixed to send period=alltime and the valid sort_field=post_date.
• New stats (android_new_stats) — hardcoded period=MONTH, sort_field=opens, so the
  Subscribers card/detail only showed the current month's top posts by opens. Fixed to
  period=ALL_TIME and sort_field=POST_DATE.

Both paths now match the web request (period=alltime, sort_field=post_date,
sort_order=desc), so the newest emailed posts appear first.

The new-stats Subscribers Emails card now also requests 10 entries (was 5), matching the
web, so more recent posts are visible without opening the detail list.

Testing instructions

Subscriber email stats show recent posts:

1. Open the Jetpack app on a site with recently emailed posts.
2. Go to Stats → Subscribers → Emails.

• Verify the most recently emailed post appears in the card and matches the web ordering (newest first).
• Verify the card shows up to 10 email entries.

3. Tap "View all" to open the Emails detail list.

• Verify the list is ordered by date (newest first) and includes the latest post.

[dangermattic]

	1 Warning
⚠️	PR is not assigned to a milestone.

Generated by 🚫 Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Android by scanning the QR code below to install the corresponding build.

	App Name	WordPress Android
	Build Type	Debug
	Version	pr23220-226b660
	Build Number	1498
	Application ID	org.wordpress.android.prealpha
	Commit	226b660
	Installation URL	2it8ahqtq94a8

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Android by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Android
	Build Type	Debug
	Version	pr23220-226b660
	Build Number	1498
	Application ID	com.jetpack.android.prealpha
	Commit	226b660
	Installation URL	0p8a0f4okv518

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 37.93%. Comparing base (00a524f) to head (226b660).
⚠️ Report is 1 commits behind head on trunk.

Files with missing lines	Patch %	Lines
...ress/android/fluxc/persistence/InsightsSqlUtils.kt	43.75%	9 Missing ⚠️
...dpress/android/fluxc/model/stats/InsightsMapper.kt	0.00%	3 Missing ⚠️
...roid/ui/newstats/datasource/StatsDataSourceImpl.kt	0.00%	2 Missing ⚠️
...droid/fluxc/store/stats/subscribers/EmailsStore.kt	71.42%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk   #23220      +/-   ##
==========================================
+ Coverage   37.91%   37.93%   +0.02%     
==========================================
  Files        2347     2347              
  Lines      127810   127829      +19     
  Branches    17781    17781              
==========================================
+ Hits        48454    48494      +40     
+ Misses      75389    75367      -22     
- Partials     3967     3968       +1     

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[nbradbury]

@adalpari This looks good and I verified email stats match the web, but Claude found a few issues. The first issue is flagged as a "blocker" but I'm not sure about the others.

review-pr23220-cmm2141-emails-stats-2026-08-14.pdf

[adalpari]

@adalpari This looks good and I verified email stats match the web, but Claude found a few issues. The first issue is flagged as a "blocker" but I'm not sure about the others.

review-pr23220-cmm2141-emails-stats-2026-08-14.pdf

Not a real blocker since it's talking about old stats, which is not the target of the PR.
However, it's interesting that a user reported the error while migrating to the new stats, but it was not reported in the old ones 🤔

Anyway, since it seems that the error was there before, I'm also fixing it.

[adalpari]

@nbradbury I also fixed the old stats screen here

[nbradbury]