Carry the resolved script's owner (its defining node) from dispatch into
the executor so `import` resolution can be lexical (§5.5). The executing
app (`app_id`) stays the SDK isolation boundary; `script_owner` is a
separate axis — the lexical origin for imports.
- `ExecRequest.script_owner: Option<ScriptOwner>` (serde default; `None`
falls back to `App(app_id)` in the engine for old payloads / cluster wire).
- `ScriptOwner` gains `Serialize`/`Deserialize` for the wire.
- The engine computes `default_origin` and hands it to the resolver
(used fully in C3; the resolve() lookup already uses it).
- Every dispatch site sets it from the resolved `Script.owner()`:
the 4 dispatcher arms (queue/trigger/http/invoke_async, via a new
`ResolvedTrigger.script_owner`), the orchestrator id-bypass, and the
`invoke()` SDK path (new `ResolvedScript.owner`, so a group script
invoked by an app resolves imports from the group).
Behaviour-preserving: app scripts still resolve `App(app_id)`; group
scripts can't yet carry imports (lifted in C4).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>