v0.20261006.0

What's Changed

• observer: Reduce CCADB prober memory usage by @beautifulentropy in #9062
• Add new MTCB service to build MTCs from db and tree by @aarongable in #8986
• mtca: sign and store one big subtree in sequence() by @ezekiel in #9061
• improve errors from health checking by @jsha in #9065
• tiles_test: fix half-open interval notation in comment. by @ezekiel in #9070
• core/mtca/mtcb: Add and use Encode/DecodeMTCSerial() by @beautifulentropy in #9071
• treedb: Stop passing **CheckpointModel to borp by @beautifulentropy in #9076
• pkimetal: don't reuse connections by @jsha in #9063
• mtca: use treedb in place of *borp.DbMap by @jsha in #9068
• Add basic gitattributes file: by @ezekiel in #9080
• wfe: send GetOrder via RA by @jsha in #9074
• subtree: add HashFromProof by @jsha in #9081
• trees: add MaxSize constant and enforce it by @jsha in #9087
• build(deps): bump github/codeql-action/init from 4.37.8 to 4.38.2 by @dependabot[bot] in #9077
• ceremony: update max validity checks for CP/CPS v6.2 profiles by @Preston12321 in #9089

Full Changelog: v0.20260928.1...v0.20261006.0