Issue #3627952: Refresh the codebase metrics pages after the set domain source action fix

Follow-up to !473 (merged) for #3627952.

#3627950 (!472 (merged)) merged into 4.x after !473 (merged) measured the codebase metrics, so docs/metrics.md and its French and Spanish translations no longer matched the branch. This regenerates them from the current 4.x head with the same measurement (cloc 2.08 over git ls-files, leaving out .tugboat/ and the metrics pages): 485 files, 34,711 lines of code. Only the figures change; the prose and the Methodology section are untouched, and the cloc command the Methodology gives reproduces the new totals.

This has to be the last change merged into 4.x before the release is tagged, or the pages go out of date again.

AI-Generated: Yes (Claude Code was used to regenerate these pages. I reviewed them before posting.)