Add catalog pages for single package URLs

[Copilot]

Single package URLs (e.g., /react, /angular) currently compare a package to itself, which is not useful. This adds catalog/index pages that show ~16 sensible version diffs instead.

Changes

Catalog link generation (src/lib/catalog/generateCatalogLinks.ts)

• Algorithm generates up to 5 major, 5 minor, and 5 patch version diffs
• Major diffs compare last version of previous major to first version (X.0.0) of next major
• Minor diffs compare last version of previous minor to first version (X.Y.0) of next minor
• Patch diffs compare consecutive patch versions
• Filters prerelease versions
• Backfills with additional diffs if fewer than 16 are found

Catalog page (src/app/[...parts]/_catalog/CatalogPage.tsx)

• Displays package name and grouped diff links
• Three sections displayed in order: Patch, Minor, Major Version Updates
• Uses prefetch={false} to prevent preloading all diffs on page load

Routing (src/app/[...parts]/page.tsx)

• Detects single package input before calling destination()
• Fetches versions and generates catalog links
• Renders catalog page for single packages, diff page for comparisons

Example

Visiting /react now shows:

• Patch: 19.2.2 → 19.2.3, 19.2.1 → 19.2.2, ...
• Minor: 19.1.4 → 19.2.0, 18.2.0 → 18.3.0, ...
• Major: 18.3.1 → 19.0.0, 17.0.2 → 18.0.0, ...

Original prompt

I want to create "catalog" or "index" pages. so if I go to /react or /angular, instead of producing a diff that compares to itself, I want to show a page which shows a number of links to some diffs we can guess. look at the logic in the autocomplete which versions we pick. bur we want more on the catalog page. maybe show like the last 5 patch versions(all compared with previous patch), and last 5 minor(all compared with previous minor) and last 5 major (all compared with the major before). make sure the links do not preload as that would create way too many diffs if you first load the page.

let's say the catalog shows 16 links, using some clever method to keep looking until we have 16 links. sometimes packages will not have that many patch or minor or major, but make some combination of "sensible" diffs until you have 16

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Project	Deployment	Review	Updated (UTC)
npm-diff	Ready	Preview, Comment	Jan 25, 2026 2:29pm

[oBusk]

@copilot don't commit any changes to next-env.d.ts

Major diffs should be from the last version of a major span, to the first of next. So find <19 and diff to 19.0.0. diff <18 to 18.0.0. I want to see a diff between for example 18.3.4...19.0.0 or 17.9.4 and 18.0.0.

The diffs between minor should be from last minor to the first minor in the next. From 18.3.4 to 18.4.0 for example.

Show patch examples first on the catalog page.

[Copilot]

@copilot don't commit any changes to next-env.d.ts

Major diffs should be from the last version of a major span, to the first of next. So find <19 and diff to 19.0.0. diff <18 to 18.0.0. I want to see...

Fixed in commit 0f880ce:

• ✅ Reverted next-env.d.ts changes (auto-generated file)
• ✅ Major diffs now compare last version of previous major to first version (X.0.0) of next major
  • Example: 18.3.1 → 19.0.0, 17.0.2 → 18.0.0
• ✅ Minor diffs now compare last version of previous minor to first version (X.Y.0) of next minor
  • Example: 19.1.4 → 19.2.0, 18.2.0 → 18.3.0
• ✅ Patch section is now shown first on catalog page

Screenshot: https://github.com/user-attachments/assets/2c209915-62be-4693-9c97-c2e38775e0cc

[oBusk]

Closed in favour of #1040