fix(replace-links): preserve unclosed fenced code blocks

Why:
- Markdown treats an opening fenced code block without a closing fence as code through the end of the document.
- Automatic linking was still processing that content as normal text, which could turn code block contents into wiki links.

What:
- Extract fenced code blocks before heading, callout, table, and link replacement processing.
- Preserve unmatched fenced blocks through EOF and restore them unchanged after replacement.
- Add regression coverage for unclosed code blocks, including when heading protection is enabled.

src/replace-links/__tests__/replace-links.code.test.ts

@@ -44,4 +44,47 @@ describe("ignore code", () => {
         })
         expect(result).toBe("```typescript\nexample\n```")
     })
+
+    it("unclosed code block", () => {
+        const settings = {
+            scoped: false,
+            baseDir: undefined,
+        }
+        const { candidateMap, trie } = buildCandidateTrieForTest({
+            files: [{ path: "example" }, { path: "typescript" }],
+            settings,
+        })
+        const result = replaceLinks({
+            body: "```typescript\nexample",
+            linkResolverContext: {
+                filePath: "journals/2022-01-01",
+                trie,
+                candidateMap,
+            },
+            settings,
+        })
+        expect(result).toBe("```typescript\nexample")
+    })
+
+    it("unclosed code block when headings are ignored", () => {
+        const settings = {
+            scoped: false,
+            baseDir: undefined,
+            ignoreHeadings: true,
+        }
+        const { candidateMap, trie } = buildCandidateTrieForTest({
+            files: [{ path: "example" }, { path: "typescript" }],
+            settings,
+        })
+        const result = replaceLinks({
+            body: "```typescript\nexample",
+            linkResolverContext: {
+                filePath: "journals/2022-01-01",
+                trie,
+                candidateMap,
+            },
+            settings,
+        })
+        expect(result).toBe("```typescript\nexample")
+    })
 })

src/replace-links/replace-links.ts

@@ -165,6 +165,58 @@ const extractLinkParts = (
     return { linkPath: canonicalPath, alias: "", hasAlias }
 }
 
+const escapeRegExp = (text: string): string =>
+    text.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")
+
+const extractFencedCodeBlocks = (
+    body: string,
+): { body: string, codeBlocks: Array<{ placeholder: string, content: string }> } => {
+    if (!body.includes("```") && !body.includes("~~~")) {
+        return { body, codeBlocks: [] }
+    }
+
+    const codeBlocks: Array<{ placeholder: string, content: string }> = []
+    let result = ""
+    let cursor = 0
+    let codeBlockIndex = 0
+
+    const openingFencePattern = /^ {0,3}(`{3,}|~{3,})[^\r\n]*(?:\r?\n|$)/gm
+    let openingMatch: RegExpExecArray | null
+
+    while ((openingMatch = openingFencePattern.exec(body)) !== null) {
+        const start = openingMatch.index
+        if (start < cursor) {
+            continue
+        }
+
+        const openingFence = openingMatch[1]
+        const fenceChar = openingFence[0]
+        const fenceLength = openingFence.length
+        const closingFencePattern = new RegExp(
+            `^ {0,3}${escapeRegExp(fenceChar)}{${fenceLength},}[ \\t]*(?:\\r?\\n|$)`,
+            "gm",
+        )
+        closingFencePattern.lastIndex = openingMatch.index + openingMatch[0].length
+        const closingMatch = closingFencePattern.exec(body)
+        const end = closingMatch
+            ? closingMatch.index + closingMatch[0].length
+            : body.length
+
+        const placeholder = `__CODE_BLOCK_${codeBlockIndex}__`
+        codeBlocks.push({
+            placeholder,
+            content: body.slice(start, end),
+        })
+        result += body.slice(cursor, start) + placeholder
+        cursor = end
+        codeBlockIndex++
+        openingFencePattern.lastIndex = end
+    }
+
+    result += body.slice(cursor)
+    return { body: result, codeBlocks }
+}
+
 // Self-linking Prevention
 const isSelfLink = (
     candidateData: CandidateData,
@@ -945,14 +997,17 @@ export const replaceLinks = ({
         })
     }
 
+    // Extract and protect fenced code blocks before any other block-level rules.
+    const { body: bodyAfterCodeBlocks, codeBlocks } = extractFencedCodeBlocks(body)
+
     // Extract and protect headings first
     const headingPattern = /^#{1,6}\s+.*$/gm
     const headings: Array<{ placeholder: string, content: string }> = []
     let headingIndex = 0
 
-    let bodyAfterHeadings = body
+    let bodyAfterHeadings = bodyAfterCodeBlocks
     if (settings.ignoreHeadings) {
-        bodyAfterHeadings = body.replace(headingPattern, (match) => {
+        bodyAfterHeadings = bodyAfterCodeBlocks.replace(headingPattern, (match) => {
             const placeholder = `__HEADING_${headingIndex}__`
             headings.push({ placeholder, content: match })
             headingIndex++
@@ -1044,5 +1099,10 @@ export const replaceLinks = ({
         resultBody = resultBody.replace(placeholder, content)
     }
 
+    // Restore fenced code blocks
+    for (const { placeholder, content } of codeBlocks) {
+        resultBody = resultBody.replace(placeholder, content)
+    }
+
     return resultBody
 }