test(frontend): cover mediaSrc, changelog, and timeline grouping

Unit tests for three previously-untested pure functions: mediaSrc's
UI Lab path handling, getChangelogForVersion's version normalization,
and groupImages' date bucketing/sorting.

src/changelog.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from 'vitest'
+import { getChangelogForVersion } from './changelog'
+
+describe('getChangelogForVersion', () => {
+  it('returns null for a null/undefined version', () => {
+    expect(getChangelogForVersion(null)).toBeNull()
+    expect(getChangelogForVersion(undefined)).toBeNull()
+  })
+
+  it('never surfaces the in-progress Unreleased section', () => {
+    expect(getChangelogForVersion('Unreleased')).toBeNull()
+    expect(getChangelogForVersion('unreleased')).toBeNull()
+  })
+
+  it('returns null for a version with no matching entry', () => {
+    expect(getChangelogForVersion('99.9.9')).toBeNull()
+  })
+
+  it('resolves a plain released version', () => {
+    const entry = getChangelogForVersion('0.1.1')
+    expect(entry?.version).toBe('0.1.1')
+    expect(entry?.date).toBe('2026-06-23')
+  })
+
+  it('strips a leading "v" from the version string', () => {
+    expect(getChangelogForVersion('v0.1.1')?.version).toBe('0.1.1')
+  })
+
+  it('strips dev/UI-lab build suffixes so they resolve to the base version', () => {
+    expect(getChangelogForVersion('0.1.1-dev')?.version).toBe('0.1.1')
+    expect(getChangelogForVersion('0.1.1-ui')?.version).toBe('0.1.1')
+    expect(getChangelogForVersion('0.1.1-beta.1')?.version).toBe('0.1.1')
+  })
+})