[xiaolai]

Summary

In WYSIWYG mode, Find could not match text across a soft line break: the break is stored as "\n" inside the paragraph's text, but it renders as a space, so a query such as a chat assis found nothing. Outside code blocks, the text being searched now reads each soft break as a space. The swap is one character for one, so match positions stay exact for highlighting, navigation, Replace and Replace All.

Policy Gates (Required)

• This PR is single-focus (one issue, one problem, one objective).
• This PR includes 100% test coverage for changed behavior and changed code paths.
• If this is a bug fix, the linked issue contains detailed reproduction context.

Linked Issue

• Fixes [Bug] Find can't match text across a soft line break #1590

Type of Change

• Bug fix
• Feature
• Docs
• Refactor
• Test-only
• Other

What Changed

• src/plugins/search/findMatches.ts: soft breaks are treated as spaces in prose before matching; code blocks (spec.code) keep "\n". The header's key decisions are updated.
• src/plugins/search/findMatches.test.ts: 7 regression tests — literal, whole-word and regex queries; a break inside bold text; Replace consuming the break; code-block newlines unaffected; hard breaks still not matching; a document parsed through the real markdown pipeline with the StarterKit schema (fails without the fix, passes with it).
• Behaviour note: in regex mode, \n no longer matches a soft break in prose (it reads as a space, as the user sees it); \s and a literal space both match it. Source mode is unchanged: there the newline is a visible line break.
• Codex audit: 1 iteration, zero findings.

Validation

• I ran pnpm check:all locally.
• I added or updated tests to fully cover behavior changes.
• I manually verified critical flows. (Not run in the live app; covered by the real-pipeline test.)

UI Evidence (if applicable)

Not applicable — no visible UI change.

PR Checklist

• The PR avoids unrelated refactors or cleanup.
• The issue context is clear (linked issue or explanation above).
• Docs/changelog were updated if behavior or usage changed. (The Search & Replace guide makes no claim about line breaks; nothing to update.)
• I am ready to address review feedback.