fix(api): correct joinTags space replacement

[Begarudev]

Purpose / Description

Fix Utils.joinTags() so spaces inside a tag are replaced with underscores
before joining.

Fixes

• Fixes Bug: Utils.joinTags() discards replace result, tags with spaces are not underscore-escaped #20628

Approach

Use the result of replace() when joining tags, and add a regression test
for tags containing spaces.

How Has This Been Tested?

• Added a regression test for tags containing spaces
• :api:testDebugUnitTest

Learning (optional, can help others)

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[Copilot]

Pull request overview

This PR fixes a bug in the API module’s Utils.joinTags() helper so that spaces within individual tags are converted to underscores before tags are concatenated into the space-delimited tag string expected by Anki/AnkiDroid.

Changes:

• Fix Utils.joinTags() to actually use the result of replace() when building the joined tag string.
• Add a regression unit test covering tags that contain spaces.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
api/src/main/java/com/ichi2/anki/api/Utils.kt	Updates joinTags() to replace spaces within each tag before joining.
api/src/test/java/com/ichi2/anki/api/ApiUtilsTest.kt	Adds a regression test asserting space-to-underscore escaping for tags.

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[ZornHadNoChoice]

#20630 (comment)

[david-allison]

Missed this. Banned.