ci: install reusable lint workflow

[topcoder1]

Adds actionlint (catches GHA-specific bugs in .github/workflows/*.yml) and prettier --check (markdown glob: **/*.md) on every PR.

Calls the reusable workflow at https://github.com/topcoder1/ci-workflows/blob/main/.github/workflows/lint.yml.

🤖 Installed via install-lint.sh.

[claude]

Supply-chain risk: mutable ref on external workflow

@main is a mutable branch — if topcoder1/ci-workflows is ever compromised or accidentally force-pushed, this workflow will silently pick up the changed code on the next CI run with no review in this repo.

Pin to an immutable commit SHA instead:

Suggested change

	uses: topcoder1/ci-workflows/.github/workflows/lint.yml@main
	uses: topcoder1/ci-workflows/.github/workflows/lint.yml@<FULL_40_CHAR_SHA>

Run git ls-remote https://github.com/topcoder1/ci-workflows refs/heads/main to get the current SHA, then keep it in sync via Dependabot (update-type: digest) or a manual bump PR. GitHub's own security hardening guide recommends pinning any uses: that targets code outside the current repo to a full commit SHA.

[claude]

Flagged 1 issue inline: reusable workflow pinned to @main on an external repo — should use a full commit SHA to avoid supply-chain risk. All other changes are markdown prettier normalization with no logic or security concerns.