CI link checker blocks PRs with pre-existing broken links on unrelated pages

[BigLep]

Problem

The linkChecker CI job currently runs across the entire repo on every PR. This means any PR touching even one file fails CI if any page anywhere in the repo has a broken external link — including pages the PR never touched.

As of today, these broken links are failing every PR:

File	Broken link	Error
builder-cookbook/data-storage/retrieve-data.md	saturn.tech	Network error
storage-providers/filecoin-deals/return-on-investment.md	calc.filecoin.eu	Network error
storage-providers/basics/quickstart-guide.md	calc.filecoin.eu	Network error
smart-contracts/fundamentals/the-fvm.md	saturn.tech	Network error
smart-contracts/advanced/oracles.md	eoracle.gitbook.io	404
builder-cookbook/data-storage/store-data.md	docs.lighthouse.storage	404
basics/how-storage-works/storage-onramps.md	singularity.storage, ramo.io	525 / 404
storage-providers/infrastructure/network.md	saturn.tech	Network error
reference/general/README.md	ramo.io, singularity.storage	404 / 525
smart-contracts/developing-contracts/solidity-libraries.md	docs.0x.org	404
storage-providers/filecoin-deals/auxiliary-services.md	saturn.tech	Network error
basics/how-storage-works/filecoin-plus.md	fidl.tech	404
smart-contracts/advanced/multisig.md	help.safe.global	404

This is not a fair burden to place on contributors. A PR fixing docs on one page shouldn't be responsible for broken links across the entire repo.

Proposed Solution

1. PR link checker — scope to changed files only

Change the CI link check on PRs to only check files changed in the PR (e.g., using git diff --name-only against the base branch). This ensures PRs are only responsible for links on pages they actually touch.

2. Scheduled weekly link check — repo-wide

Add a weekly scheduled workflow (e.g., GitHub Actions schedule: cron) that runs the full repo-wide link check and automatically opens or updates an issue with the results. This keeps the repo's link health visible without blocking contributors.

3. Fix the current broken links (separate cleanup PR)

The 13 broken links above should be fixed or removed in a dedicated PR, independent of any feature work.

[BigLep]

I feel like this was maybe covered elsewhere, but I can't find it. Please close if this is a duplicate.