SOP: Validate a sitemap before you ever submit it

SOP: Validate a sitemap before you ever submit it
Catch errors locally so GSC never logs them.

Step 1 — XML well-formedness: run xmllint --noout sitemap.xml. ✅ Exit code 0.

Step 2 — Encoding: ✅ UTF-8, no byte-order-mark (BOM breaks parsing in some crawlers).

Step 3 — ✅ Every URL is absolute, https, properly escaped (& → &, etc.).

Step 4 — Counts: ✅ ≤50,000 URLs and ✅ ≤50 MB uncompressed.

Step 5 — Tag order: loc first inside each url; optional tags after.

Step 6 — Spot-fetch 10 random loc URLs. ✅ All return 200.

Step 7 — Confirm the declared namespace matches the sitemap protocol version.

Definition of done: xmllint passes, all limits respected, 10/10 sampled URLs return 200, ampersands escaped — then submit.