Content Classification: Dynamicize taxonomy error messages

[Infinite-Null]

What?

This PR updates the error and notice messages in the Content_Classification ability to dynamically display the specific taxonomy label (e.g., "category" or "tag") rather than generic hardcoded "taxonomy" terminology.

Why?

When users interacted with specific taxonomy panels (such as "Suggest Categories" under the Categories sidebar panel), error notices displayed generic phrasing like "No taxonomy suggestions were generated." or "You do not have permission to generate taxonomy suggestions." This caused confusion as users were explicitly generating suggestions for categories.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Sonnet 4.6
Used for: Validating bug, suggesting a fix.

Testing Instructions

1. Open a Post.
2. Open the Categories accordion panel in the right sidebar.
3. Trigger Category suggestion generation with empty content or under conditions with no results/no permission.
4. Verify the notice banner displays "Content is required to generate category suggestions." or "No category suggestions were generated." (instead of generic "No taxonomy suggestions were generated.").

Screenshots or screencast

Before

Screen.Recording.2026-08-05.at.1.30.25.PM.mov

After

Screen.Recording.2026-08-05.at.1.29.48.PM.mov

Changelog Entry

Fixed - Display specific taxonomy labels (e.g. category) in Content Classification notice error messages instead of generic terminology.

[github-actions]

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Co-authored-by: Infinite-Null <ankitkumarshah@git.wordpress.org>

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[codecov]

Codecov Report

❌ Patch coverage is 84.21053% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.44%. Comparing base (5599e9d) to head (0d389bf).

Files with missing lines	Patch %	Lines
.../Content_Classification/Content_Classification.php	84.21%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #916   +/-   ##
==========================================
  Coverage      80.43%   80.44%           
- Complexity      2565     2573    +8     
==========================================
  Files            110      110           
  Lines          10448    10462   +14     
==========================================
+ Hits            8404     8416   +12     
- Misses          2044     2046    +2     

Flag	Coverage Δ
unit	80.44% <84.21%> (+<0.01%)	⬆️

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