Remove stray "AI" references from UI labels and buttons

[raftaar1191]

What does this PR do?

Removes explicit "AI" text from user-facing labels, headings, and buttons across three areas of the plugin, per #310.

Changes

• Media Library (attachment edit screen + media modal): "AI Alt Text" label → "Alt Text"
• Post editor image block (inspector panel): "AI Alternative Text" heading → "Alternative Text"
• Post editor summarization (sidebar + toolbar): "Generate AI Summary" / "Re-generate AI Summary" → "Generate Summary" / "Re-generate Summary"
• E2E tests: updated toHaveText assertions and comments to match new button text

Proof:

Alt Text Generation:

Content Summarization

Related issue

Fixes #310

Use of AI Tools

Used VS Code running Sonnet 4.6

[github-actions]

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Co-authored-by: raftaar1191 <raftaar1191@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.05%. Comparing base (71f393a) to head (5950f5c).
⚠️ Report is 5 commits behind head on develop.

Files with missing lines	Patch %	Lines
...iments/Alt_Text_Generation/Alt_Text_Generation.php	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #320   +/-   ##
==========================================
  Coverage      57.05%   57.05%           
  Complexity       591      591           
==========================================
  Files             42       42           
  Lines           3083     3083           
==========================================
  Hits            1759     1759           
  Misses          1324     1324           

Flag	Coverage Δ
unit	57.05% <0.00%> (ø)

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[jeffpaul]

Post editor image block (inspector panel): "AI Alternative Text" heading → "Alternative Text"

In reviewing this, we can likely just remove this heading as the same one appears just above and should suffice for the alt text textarea and our (re)generate button:

Post editor summarization (sidebar + toolbar): "Generate AI Summary" / "Re-generate AI Summary" → "Generate Summary" / "Re-generate Summary"

Let's go ahead and also remove the ", generated by AI" bit of the helper text as well:

[raftaar1191]

@jeffpaul Updated the PR as per your latest comment

Proof:

Alt Text Generation:

Content Summarization