fix: clear a user's presence when their account or site membership ends

[i-am-chitti]

Description

Fixes #327

Hooks deleted_user and remove_user_from_blog to clear a user's presence immediately instead of leaving rows to age out on TTL. Re-pushing the network summary falls out for free — wp_remove_user_presence() already fires the change signal the push is wired to.

Testing

• Added unit tests for both hooks in isolation, plus an integration test covering wpmu_delete_user() clearing presence across every site a user belonged to.
• Updated two existing tests (post list, REST controller) that had relied on a deleted user's row surviving deletion to exercise their own fallback-rendering paths.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Sonnet 5
Used for: Implementation and tests

[github-actions]

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Props iamchitti, joefusco.

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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 963998ce493d74f7af9bd9628539de0ae0aa616a. Auto-updates when you push.}

[josephfusco]

Base branch is gone. #299 and #313 were closed today and replaced by a stack, #332 through #337, so feature/network-presence-screen will never merge.

Retarget to main. Your commits cherry-pick clean apart from one test in tests/test-network-presence.php, which the restructure split into four files. That test asserts the re-push, so it belongs in tests/test-network-summary-push.php on #333, where it passes unchanged.

#328 has the same base problem; note on the issue.

[josephfusco]

This looks good to me. Thanks for adding!