scriptmem: Execute — one entry, backend-routed, tagged Outcome

[vinodhalaharvi-claude]

What

The unified execution entry that hides the backend split behind a single call. A front end hands over prose (+ discovery + an LLM) and gets back an Outcome that is either a finished in-memory result or a temporal plan to submit. The front end branches only on the Outcome's execution shape — never on the grammar, the verbs, or the backend keyword.

Execute(ctx, complete, GrammarInfo, MemoryConfig, prose) → Outcome
  translate (LLM) → parse → resolve → inspect backend → either:
    memory   : RunMemory in-process      → Outcome{Memory, Result}
    temporal : Compile to a durable plan → Outcome{Temporal, Plan}

The tagged Outcome

Outcome{ Backend, Result, Plan } — Backend selects which arm is meaningful (Result for memory, Plan for temporal). The caller (loom) branches on Backend to pick its delivery shape — post the result now, or submit + correlate + await — learning only the execution shape, never the grammar. The backend is chosen by the DSL the LLM emits (the memory|temporal keyword), driven by the grammar prompt, not the caller.

Why it lives in scriptmem (not script)

Executing memory needs the in-process runtime + its dep tree, so the envelope that may run memory belongs with it. pkg/script stays lean (verified) — callers that only translate/compile pay nothing for the runtime; a caller that wants real execution imports scriptmem and accepts the deps, which is honest (running memory is the runtime).

Tests

• temporal program → Outcome{Temporal} with a 2-node plan, no result
• memory program routes to the runtime (asserts no plan is produced; live verb output needs credentials, covered by runtime's own tests)
• unknown verb rejected on both backends (UnknownBuiltinError) before any execution — safety net through the envelope
• historical verb on temporal → NotImplementedOnBackendError, no plan

Step	Result
go vet / gofmt / staticcheck	✅
go test -race ./...	✅
go build ./...	✅
pkg/script stays lean	✅

⚠️ Known follow-up (not this PR)

Found while testing: the catalog marks echo memory-capable, but the in-memory runtime has no echo case, so memory static ( echo ) resolves then fails at runtime ("unknown action: echo"). The catalog and the runtime's actual verb set are slightly misaligned (echo is effectively temporal-only). Worth a small reconciliation PR — either add echo to the runtime or mark it temporal-only in the catalog.

Next

loom's memory-routing branch: import scriptmem, call Execute, branch on Outcome.Backend — post Result immediately (memory) or submit Plan + correlate + await (temporal, today's path). That's the last mile: prose in Slack → actually runs.