fix(site): regenerate the lockfile after the pin/maintenance collision

Two Renovate MRs landed four seconds apart on 2026-08-06: lock-file-maintenance regenerated the whole lockfile, then pin-dependencies merged a diff computed against the pre-maintenance file. The result pins @astrojs/check 0.9.9 while the transitive graph still describes 0.9.0, so npm ci fails and main has been red since (build-docs runs only on main). Lockfile regenerated; npm ci and the full site build verified locally.