The epic's combined scope and technical design document, one doc with a WRITING ticket carrying it. Part of CLOUDP-437684 (Package and test search extensions beyond AL2023 on v9.0). Settles, before implementation starts:

• the bazel threading shape: config groups per Linux release family mapping to the glibc-floor artifact, and what AL2 and non-Linux exclusion looks like in the selects
• package layout for rpm/deb: install paths for the extension pair, and where a packaged mongod expects sharedLibraryPath to point
• the presence-check design: one source of truth shared with the archive mapping, so adding a platform updates the check automatically
• the smoke plan and its CI cost: dedicated secure-mode variants per platform (the existing release variants cannot host the extension suites - they forbid experimental-tagged tasks, and their secure compile flag drops in patch builds), which arch(es) per family, and cadence
• agreement with the extension-side Scope/TD (CLOUDP-437687) on the variant key name, since resmoke, the download rules, and the archive mapping all consume it

Acceptance: the doc exists and carries sign-off from server query integration and the packaging owners; the WRITING ticket links the doc through its Document-link field.

Depends on CLOUDP-437687 (shared variant-key decision).