feat: deterministic stub orchestrator (v0.1.0)

The orchestrator-llm module turns a goal text into a Plan JSON
that the F∆I hub can apply. v0.1.0 is a deterministic stub —
it always emits a three-step plan (explain, explain-stub-notice,
save_flow with debug.echo) regardless of the goal.

Why ship a stub: it validates the module → plan → apply pipeline
end-to-end before adding LLM integration. The output is a
structurally valid Plan that round-trips cleanly through
fai_hub::plan::Plan deserialization.

v0.2.0 will replace the stub body with an actual LLM call once
the F∆I platform exposes outbound HTTP to permitted modules via
wasi-http.

Files:
- module.yaml — capability orchestrator.plan@0.1.0, no permissions
- wit/world.wit — copy of fai:platform@0.1.0
- src/lib.rs — wit_bindgen Guest impl that delegates to plan.rs
- src/plan.rs — pure plan-builder (host + WASM compatible)
- tests/plan_compatibility.rs — plan JSON shape assertions
- rust-toolchain.toml — pin to Rust 1.86 with wasm32-wasip2 target
- README.md — usage and status

Signed-off-by: flemming-it <sf@flemming.it>

tests/plan_compatibility.rs

@@ -0,0 +1,47 @@
+//! Verify that plan JSON emitted by orchestrator-llm parses
+//! cleanly as a `fai_hub::plan::Plan`. This protects against
+//! schema drift between this module and the hub.
+//!
+//! Note: this test runs only on the host target. The WASM build
+//! does not include test harnesses.
+#![cfg(not(target_arch = "wasm32"))]
+#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+
+use orchestrator_llm::build_plan;
+use serde_json::Value;
+
+#[test]
+fn emitted_plan_has_required_top_level_fields() {
+    let json = build_plan("test goal");
+    let parsed: Value = serde_json::from_str(&json).expect("plan must be valid json");
+    assert!(parsed["schema_version"].is_u64());
+    assert!(parsed["goal"].is_string());
+    assert!(parsed["steps"].is_array());
+}
+
+#[test]
+fn each_step_has_kind_tag() {
+    let json = build_plan("test goal");
+    let parsed: Value = serde_json::from_str(&json).unwrap();
+    for step in parsed["steps"].as_array().unwrap() {
+        assert!(step["kind"].is_string(), "step missing kind tag: {step}");
+    }
+}
+
+#[test]
+fn save_flow_step_yaml_parses_as_flow_definition() {
+    // The save_flow step embeds a YAML flow body. Verify it
+    // round-trips through serde_yaml.
+    let json = build_plan("anything");
+    let parsed: Value = serde_json::from_str(&json).unwrap();
+    let save_flow_step = parsed["steps"]
+        .as_array()
+        .unwrap()
+        .iter()
+        .find(|s| s["kind"] == "save_flow")
+        .expect("expected a save_flow step");
+    let yaml_text = save_flow_step["yaml"].as_str().unwrap();
+    let flow: Value = serde_yaml::from_str(yaml_text).expect("embedded yaml must parse");
+    assert_eq!(flow["name"], "orchestrator-stub-greeting");
+    assert!(flow["steps"].is_array());
+}