create --type addition
add: `spt-bundled-adapters.tar.gz` — claude-spt + PACER ride the release set as a seed source
Milestone body item (releases#331): spt-core ships with inbuilt shells (PACER first); ruled at grill 2026-09-23 to also carry claude-spt, as a BUNDLE asset rather than bytes in the binary.

Shape (CONTEXT.md "bundled adapters"): one signed update-set asset `spt-bundled-adapters.tar.gz` beside `spt-docs.tar.gz`, holding each member's published `.spt` (claude-spt, PACER) at whatever version was current when the spt-core release was cut. It is a SEED SOURCE, not a pin: apply installs a member that is absent and offers one newer than the installed copy exactly as a peer would; never downgrades; a member keeps its own `[update]` avenue (gh_release) and peer propagation, and its version is not tied to the core release. Nothing bundled auto-spawns. The bundle rides peer propagation with the set (the releases#330 docs leg generalised: `FetchAsset`), and is retained in the release cache after landing so a peer can serve it. `adapter list` marks members `(built-in)`.

Release side: the release workflow fetches the members' latest published archives at cut time and lists the asset in `update-set.json` with its sha256 under the signed metadata.

Gate: unit on the install/offer/never-downgrade decision; int: a fresh SPT_HOME applying a set with the bundle ends with both adapters registered; a node holding a newer claude-spt is left alone.