[Artifact Forest 3/9] Add bounded scripttool screenplay conversion adapter

[szmyty]

Parent: #421
Depends on: #423

Provider candidate: https://github.com/rsdoiel/scripttool

Outcome

Adopt/adapt/reject scripttool as a bounded external screenplay conversion provider and, if adopted, expose its proven conversions through the canonical graph.

Observed upstream CLI surface includes:

• FDX → Fountain
• FadeIn → Fountain
• OSF → Fountain
• Fountain → FDX
• Fountain → FadeIn
• Fountain → OSF
• Fountain → JSON
• Fountain formatting
• Fountain character reporting

Requirements

• Evaluate current source/version/release/install status and AGPL-3.0 obligations.
• Keep the provider external: do not vendor or link AGPL code into MIT-licensed Renderflow core.
• Register stable provider/tool and capability IDs.
• Probe exact version/runtime availability.
• Invoke directly with bounded argv, timeout, capture, cancellation, and expected-output checks.
• Validate output independently against [Artifact Forest 2/9] Define canonical screenplay artifacts and capability truth #423 fixtures/schema.
• Record source/output hashes, provider version, argv digest, loss profile, and validation evidence.
• Model each supported direction as a separate graph edge.
• Reject unsupported/unknown behavior instead of falling back silently.

Acceptance criteria

• At least the six FDX/FadeIn/OSF ↔ Fountain routes are independently proven or explicitly rejected with evidence.
• Fountain → JSON is represented as an inspection/derivative capability rather than a magical canonical truth.
• Missing/incompatible provider is excluded during planning with an actionable diagnostic.
• Provider failure cannot leave a successful artifact/checkpoint.
• Fixtures cover malformed inputs and representational loss.
• Licensing/distribution notes are present in the tool registry and docs.

Non-goals

Bundling scripttool into Renderflow distributions or claiming lossless round-trip for every screenplay feature.

Provider observation — 2026-09-25

The current public scripttool README documents explicit CLI commands for:

• FDX → Fountain
• FadeIn → Fountain
• OSF → Fountain
• Fountain → FDX
• Fountain → FadeIn
• Fountain → OSF
• Fountain → JSON
• Fountain formatting and a character-list report

The repository is not archived, but its checked-in license is AGPL-3.0. Treat it as an external command provider; do not vendor/link it into Renderflow core. Re-verify current release/install viability during implementation.