Make `import` resolution lexical (§5.5): an inherited group script's
imports resolve against the module set at its OWN defining node, walking
up from there — a leaf app can't shadow them, and a group script behaves
identically under every inheriting app.
Mechanism — Rhai's `_source` carries the importing AST's origin tag:
- The entry script has no source tag → resolve from `default_origin` (its
defining node, threaded in via C2).
- Each resolved module's AST source is set to `encode(module.owner())`
before `eval_ast_as_new`, so its nested `import`s carry the module's own
node as `_source` and resolve from there — lexical chaining.
- `encode_origin`/`decode_origin` map a `ScriptOwner` to/from `app:<uuid>`
/ `group:<uuid>`.
Cache rekeyed from `(app_id, name)` to the resolved `ScriptId`: a compiled
module is lexically self-contained, so its body is a pure function of
`(script_id, updated_at)` — this also dedupes a shared group module across
inheriting apps and keeps same-named cross-app modules distinct.
Adds two executor-core unit tests (origin-keyed fake) proving the trust
boundary: a group module's import binds the group's module even when an
app-owned module of the same name exists; `ScriptOwner` gains `Hash`.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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