Patch series refactor

The merged dsh-v0.2.1-rc.2 maintenance source contains 41 active patches. Its legacy IDs intentionally retain historical gaps (004, 006, 008, ... 048) because the IDs are embedded in Studio-Patch commit trailers and are bound to the reviewed maintenance bundle, source descriptor, commit inventory, and patch content hashes.

This branch adds a canonical contiguous sequence field (1..41) to manifest.json and validates it with scripts/check-patch-sequence.mjs. The legacy id and filename remain unchanged, so the maintenance bundle stays cryptographically verifiable and can still be regenerated from the pinned DSH source.

A future full renumbering must be a maintenance-source migration, not a file rename. It must:

Export a new linear maintenance branch from the pinned DSH baseline.
Rewrite each Studio-Patch trailer and regenerate every patch diff.
Rebuild maintenance.bundle, source.json, and all SHA-256 inventories.
Update historical documentation and downstream references.
Run source, manifest, bundle, host, package, and update qualification gates.

Until that migration is complete, the canonical sequence is the safe way to present patches in UI and release documentation while preserving rollback and upstream-removal evidence.