feat: move inline heartbeat JS to a standalone enqueued script

[i-am-chitti]

Description

Currently, the script handling heartbeat pings is outputted directly as a multi-line HEREDOC string inside wp_presence_enqueue_heartbeat_ping() via wp_add_inline_script(). This brings a few challenges:

1. It shows up as an anonymous inline script in browser DevTools, making setting breakpoints or debugging in the Sources panel extremely difficult.
2. The script cannot be cached independently by browsers.
3. Code linters and formatters cannot easily lint or clean the script.

This PR addresses this by:

• Moving the core JavaScript out of includes/heartbeat.php to a new standalone file assets/js/presence-ping.js.
• Registering and enqueuing the script using wp_enqueue_script() with jquery and heartbeat as dependencies.
• Passing the dynamic PHP-side configuration object wpPresenceConfig via wp_add_inline_script() attached to the script as a before dependency.

Fixes

• Move inline heartbeat JS to a standalone enqueued script #135

Proposed Changes

• assets/js/presence-ping.js
  • Created a new JS file containing the heartbeat presence check-in script logic.
• includes/heartbeat.php
  • Replaced the multi-line HEREDOC wp_add_inline_script() block with wp_enqueue_script() pointing to the new standalone assets file.
  • Attached the configuration wpPresenceConfig to the script handle instead.
• tests/test-heartbeat.php
  • Added test_wp_presence_enqueue_heartbeat_ping() unit test to verify that the script is enqueued and the inline configuration data is attached properly.

How to Test / Verification

Run the test suite in wp-env: 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: Extracting inline HEREDOC JavaScript into assets/js/presence-ping.js, and writing unit tests to cover script enqueuing.

[github-actions]

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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 aab2d3c085602a427c232df6dca344fe3567e962. Auto-updates when you push.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 31.08%. Comparing base (3a2ae99) to head (aab2d3c).
⚠️ Report is 26 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #169      +/-   ##
============================================
+ Coverage     28.56%   31.08%   +2.51%     
  Complexity      161      161              
============================================
  Files            15       15              
  Lines          1817     1821       +4     
============================================
+ Hits            519      566      +47     
+ Misses         1298     1255      -43     

Flag	Coverage Δ
phpunit	31.08% <100.00%> (+2.51%)	⬆️

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