refactor(github): move inline PR comment line placement to src/shared (#36904)

src/shared/github/pr-inline-comment-placement.test.ts

@@ -0,0 +1,29 @@
+import { describe, expect, it } from 'vitest'
+import type { PRComment } from './comment-types'
+import { getPRInlineCommentPlacement } from './pr-inline-comment-placement'
+
+const comment = (overrides: Partial<PRComment>): PRComment => ({
+  id: 1,
+  author: 'octocat',
+  authorAvatarUrl: '',
+  body: 'body',
+  createdAt: '2026-11-01T00:00:00Z',
+  url: 'https://github.com/o/r/pull/1#discussion_r1',
+  ...overrides
+})
+
+describe('getPRInlineCommentPlacement', () => {
+  it('places a current review comment on its range', () => {
+    expect(
+      getPRInlineCommentPlacement(comment({ path: 'src/a.ts', line: 12, startLine: 10 }))
+    ).toEqual({ path: 'src/a.ts', line: 12, startLine: 10 })
+  })
+
+  it('keeps outdated threads and conversation comments out of the diff', () => {
+    expect(
+      getPRInlineCommentPlacement(comment({ path: 'src/a.ts', line: 12, isOutdated: true }))
+    ).toBeNull()
+    expect(getPRInlineCommentPlacement(comment({ path: 'src/a.ts' }))).toBeNull()
+    expect(getPRInlineCommentPlacement(comment({}))).toBeNull()
+  })
+})

src/shared/github/pr-inline-comment-placement.ts

@@ -0,0 +1,16 @@
+import type { PRComment } from './comment-types'
+
+export type PRInlineCommentPlacement = {
+  path: string
+  line: number
+  startLine: number | undefined
+}
+
+/** Where a PR review comment sits in the current diff, or null when it should not render inline. */
+export function getPRInlineCommentPlacement(comment: PRComment): PRInlineCommentPlacement | null {
+  // Why: outdated threads keep originalLine for the sidebar, but rendering it inline can attach the comment to unrelated current code.
+  if (comment.isOutdated || !comment.path || typeof comment.line !== 'number') {
+    return null
+  }
+  return { path: comment.path, line: comment.line, startLine: comment.startLine }
+}