feat: distinguish between underline and strikethrough labels

[wuyiping0628]

PR

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our Commit Message Guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

Summary by CodeRabbit

• Bug Fixes
  • Updated strikethrough formatting implementation to use the correct HTML element for proper semantic representation of text styling.

[coderabbitai]

Walkthrough

The strikethrough formatting implementation is updated from using the u (underline) HTML element to the semantically correct s (strikethrough) element across the fluent-editor packages. Changes are applied to the format definition, stylesheet selector, and example content.

Changes

Cohort / File(s)	Summary
Strike Format Implementation packages/fluent-editor/src/formats/strike.ts, packages/fluent-editor/src/assets/editor.scss	Updated StrikeBlot.tagName from u to s and changed the corresponding SCSS selector from u.ql-custom-strike to s.ql-custom-strike for consistent strikethrough rendering.
Example Content packages/projects/src/views/yuque/YuQue.vue	Updated DEFAULT_CONTENT HTML example to use <s> tag instead of <u class="ql-custom-strike"> for strikethrough representation.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Strikethrough tales once told in u,
Now rest in s where they're due,
A semantic hop, both clean and bright,
HTML elements shining right! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: updating the strikethrough implementation to use semantic HTML tags instead of tags, which distinguishes strikethrough from underline formatting.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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• Commit unit tests in branch wyp/ol-0319

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@packages/fluent-editor/src/assets/editor.scss`:
- Around line 71-73: Restore compatibility for legacy HTML by ensuring the
.ql-custom-strike rule targets both the current element and the older 'u' tag:
add or change the selector to include u.ql-custom-strike (e.g.,
u.ql-custom-strike, s.ql-custom-strike { text-decoration: line-through; }) so
existing content using u.ql-custom-strike continues to render as strikethrough
while keeping the s.ql-custom-strike rule.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: c2f3eb1a-9d1d-4f12-9ce1-f93f1db17374

📥 Commits

Reviewing files that changed from the base of the PR and between 270a8cd and 3aab6df.

📒 Files selected for processing (3)

• packages/fluent-editor/src/assets/editor.scss
• packages/fluent-editor/src/formats/strike.ts
• packages/projects/src/views/yuque/YuQue.vue

[coderabbitai]

⚠️ Potential issue | 🟠 Major

Preserve legacy strike rendering for existing u.ql-custom-strike content.

Line 71 removes the old selector path; older stored HTML using u.ql-custom-strike will now render as underline (because of the u rule below), not strike.

💡 Suggested compatibility-safe fix

-    s.ql-custom-strike {
+    s.ql-custom-strike,
+    u.ql-custom-strike {
       text-decoration: line-through;
     }

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	s.ql-custom-strike {
	text-decoration: line-through;
	}
	s.ql-custom-strike,
	u.ql-custom-strike {
	text-decoration: line-through;
	}

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@packages/fluent-editor/src/assets/editor.scss` around lines 71 - 73, Restore
compatibility for legacy HTML by ensuring the .ql-custom-strike rule targets
both the current element and the older 'u' tag: add or change the selector to
include u.ql-custom-strike (e.g., u.ql-custom-strike, s.ql-custom-strike {
text-decoration: line-through; }) so existing content using u.ql-custom-strike
continues to render as strikethrough while keeping the s.ql-custom-strike rule.