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>

rust-toolchain.toml

@@ -0,0 +1,4 @@
+[toolchain]
+channel = "1.86"
+targets = ["wasm32-wasip2"]
+components = ["rustfmt", "clippy"]