fix: replace GROUP_CONCAT with PHP-side aggregation

[i-am-chitti]

Description

Currently, wp_get_presence_summary() and wp_get_active_rooms() both temporarily modify the MySQL session variable group_concat_max_len before performing queries with GROUP_CONCAT.

This pattern has several issues:

1. It does not work reliably in environments that pool/proxy database connections (e.g., ProxySQL, PlanetScale) because the mutated session state is not guaranteed to persist across a connection checkout.
2. In some managed environments, the database user lacks privileges to modify session variables using SET SESSION.
3. It makes the codebase dependent on MySQL-specific session operations.

Since the active presence table is small and transient, fetching the raw room and user_id rows and performing the aggregation in PHP is a highly reliable and performant alternative.

This PR implements PHP-side aggregation for:

• wp_get_presence_summary()
• wp_get_active_rooms()

Fixes

• Replace SET SESSION group_concat_max_len with PHP-side aggregation #133

Proposed Changes

• includes/functions.php
  • Removed the SET SESSION group_concat_max_len queries from both wp_get_presence_summary() and wp_get_active_rooms().
  • Updated wp_get_presence_summary() to fetch raw room and user_id columns and aggregate counts/users per prefix in PHP.
  • Updated wp_get_active_rooms() to fetch raw rows, aggregate user lists per room, sort them, and sort the active rooms list by total entry counts descending in PHP.

How to Test / Verification

Run the PHPUnit test suite:

npm run test

Verify that all unit tests pass successfully.

Use of AI Tools

AI assistance: Yes
Tool(s): Antigravity
Model(s): Gemini 3.5 Flash
Used for: Help with refactor, replace and implementing the equivalent sorting and drafting PR description.

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[github-actions]

▶ Preview in WordPress Playground

Boots a fresh WordPress with this PR's presence-api build, seeds 5 demo users, and drops you on the dashboard.

_{Stress-test variant: 40 demo users · Built from 256811818bdcc37b051440ca4536fe73924892b2. Auto-updates when you push.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 28.87%. Comparing base (3a2ae99) to head (2568118).
⚠️ Report is 26 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #170      +/-   ##
============================================
+ Coverage     28.56%   28.87%   +0.31%     
  Complexity      161      161              
============================================
  Files            15       15              
  Lines          1817     1825       +8     
============================================
+ Hits            519      527       +8     
  Misses         1298     1298              

Flag	Coverage Δ
phpunit	28.87% <100.00%> (+0.31%)	⬆️

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