Clarify global AI toggle as a master switch (#600)

[dhrupo]

What?

Closes #600

Relabels the global header toggle on Settings → AI from "Enable AI" to "AI features enabled", so the control reads as a master on/off state rather than an imperative implying it switches on every feature.

Why?

The toggle binds to a single wpai_features_enabled option and is never derived from the individual feature states, so it always renders solid-on even when only some features are enabled — misrepresenting the configuration (the reported problem). The imperative label "Enable AI" reinforced that misreading.

On the issue, @gziolo suggested the control should "reflect the state 'AI enabled'" and @dkotter agreed. This implements that with a minimal label change; the existing InfoTip next to the toggle already documents the master-switch behavior. It intentionally avoids the per-section toggles attempted in #617, which were closed as duplicative with the existing Enable all / Disable all buttons.

How?

• routes/ai-home/stage.tsx: change the global toggle's label from __( 'Enable AI', 'ai' ) to __( 'AI features enabled', 'ai' ).
• tests/e2e/utils/helpers.ts and tests/e2e/specs/admin/settings.spec.js: update the label locators, and add a regression test asserting the master toggle stays checked when a single feature is turned off (proving it is a master switch, not an aggregate).

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 4.x
Used for: Implementation, tests, and drafting this PR description — reviewed, tested, and edited by me.

Testing Instructions

1. Go to Settings → AI.
2. Confirm the header control reads "AI features enabled" (not "Enable AI").
3. Enable AI, then enable only a subset of features; confirm the control still reads as a master switch (hover the info icon to see it governs all features).
4. Toggle a single feature off and confirm the master control is unaffected.

Screenshots or screencast

Before	After
Header control labeled "Enable AI"	Header control labeled "AI features enabled"

Changelog Entry

Changed - Settings: the global AI control is now labeled "AI features enabled" to clarify it is a master switch rather than a summary of individual feature states.

[github-actions]

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Co-authored-by: dhrupo <dhrupo@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>
Co-authored-by: gziolo <gziolo@git.wordpress.org>

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.48%. Comparing base (ea79289) to head (d70a6d0).

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #798   +/-   ##
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  Coverage      76.48%   76.48%           
  Complexity      1869     1869           
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  Files             89       89           
  Lines           7990     7990           
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  Hits            6111     6111           
  Misses          1879     1879           

Flag	Coverage Δ
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[dkotter]

@dhrupo Thanks for the PR. Can you ensure the PR description follows our template? Looks like multiple sections are missing or are incomplete right now: https://github.com/WordPress/ai/blob/develop/.github/PULL_REQUEST_TEMPLATE.md

[dhrupo]

@dkotter thanks for the review! I've updated the description to follow the PR template — all sections are now filled in (What / Why / How / Use of AI Tools / Testing Instructions / Screenshots / Changelog Entry). Let me know if anything still looks incomplete.

[dkotter]

If we're going to update this label, I think it needs to be dynamic depending on the state. For example, if I have things globally disabled, the label now says AI features enabled, which is incorrect:

I personally don't think we need to change what we have but if we are going to change the label, I'd suggest we make that dynamic based on the toggle state and have it be either AI enabled or AI disabled

Any thoughts on this @jeffpaul?

[jeffpaul]

Punting out a release to continue discussion on the linked issue from #600 (comment).