Content Classification: Fix minimum-content threshold for CJK languages

[i-anubhav-anand]

What?

Closes #571

Make the content classification minimum-content threshold locale-aware for CJK languages (Chinese, Japanese, Korean).

Why?

CJK text has no word boundaries — count(text, 'words') from @wordpress/wordcount always returns 0 for Japanese/Chinese. With the 150-word threshold hard-coded, the "Suggest Tags/Categories" button stays permanently disabled for CJK users regardless of how much content they write.

How?

• Added a CJK_REGEX that matches CJK Unified Ideographs, Hangul, and fullwidth punctuation (/[　-鿿가-퟿！-｠]/).
• When the post content contains CJK characters, the threshold is evaluated with 'characters_excluding_spaces' instead of 'words'. The 150 minimum is reused; 150 characters is a reasonable proxy for "enough content" in CJK scripts.
• Exported hasCJKContent from the hook so SuggestionPanel can adapt the hint text: "approximately 150 characters" for CJK content, "approximately 150 words" otherwise.

Note: instead of the locale-based _x() approach referenced in the issue, this uses runtime content detection, which works for multilingual posts and requires no translator intervention.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): claude-sonnet-4-6
Used for: Implementation assistance; code reviewed and verified by me.

Testing Instructions

1. Set site language to Japanese (Settings → General → Site Language).
2. Open a post, paste こんにちは。 ~30 times in the content area.
3. Open the Tags or Categories panel in the sidebar.
4. Confirm the "Suggest Tags" button becomes enabled (previously always disabled for CJK).
5. Verify the hint text says "approximately 150 characters" not "approximately 150 words".
6. Switch back to English, add fewer than 150 words — confirm hint says "approximately 150 words".

Screenshots or screencast

N/A — the change is functional (button enables/disables correctly) and the hint text adapts.

Changelog Entry

Fixed - Content Classification: minimum-content threshold now uses character count for CJK languages (Chinese, Japanese, Korean) so the "Suggest Tags/Categories" button correctly enables for CJK content. The hint text adapts to say "approximately 150 characters" for CJK content.

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[dkotter]

One, this is opened against trunk, not develop. Two, this seems to just be a duplicate of #716 which we already ask to be closed as it itself was already a duplicate. As such, closing this out but let me know if I'm missing something here