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>

module.yaml

@@ -0,0 +1,31 @@
+schema_version: 1
+name: orchestrator-llm
+version: 0.1.0
+
+# Capability provided by this module.
+provides:
+  - capability: orchestrator.plan
+    version: 0.1.0
+
+# Inputs the invoke function accepts.
+inputs:
+  goal: text
+  # Optional JSON-encoded list of installed capabilities. If
+  # omitted or empty, the module plans without capability context.
+  available_capabilities: text
+  # Optional JSON-encoded list of all known store capabilities
+  # (installed + planned + alpha). Used when the orchestrator
+  # needs to suggest installations.
+  store_capabilities: text
+
+# Outputs produced.
+outputs:
+  # JSON-encoded Plan compatible with `fai_hub::plan::Plan`.
+  plan: json
+
+# Permissions required.
+#
+# v0.1.0 is a deterministic stub — no network, no fs, no env.
+# v0.2.0 will add `net: <llm-endpoint>` once the platform exposes
+# wasi-http to permitted modules.
+permissions: []