feat(sdk): Context::emit for WIT 1.1 host.emit-event (T1)

Brings the module SDK to WIT 1.1 in lockstep with the platform and
exposes the new host.emit-event as an ergonomic ctx.emit(name,
payload). Modules emit ephemeral progress/stream events (progress,
token streaming) delivered live to a following client and never
persisted.

- wit/world.wit → 1.1.0 (host.emit-event + use types.{payload}).
- host.rs: an emit hook (thread-local fn pointer; guest is
  single-threaded). The #[fai_module] expansion installs a closure
  reaching the real WIT emit-event import at the start of each
  invocation; Context::emit calls through it. Outside a hub (unit
  tests) it is a silent no-op.
- examples/progress: reference module emitting progress + token events;
  builds clean for wasm32-wasip2, proving the ergonomics end-to-end.

The SDK keeps shielding module authors: emit is the whole surface, no
wit_bindgen in sight.

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

examples/progress/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "progress_example"
+version = "0.1.0"
+edition = "2024"
+license = "Apache-2.0"
+publish = false
+description = "Reference module showing WIT 1.1 host.emit-event via ctx.emit (progress + token streaming)."
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+chain-module-sdk = { path = "../../crates/chain-module-sdk" }
+
+[profile.release]
+opt-level = "s"
+lto = true
+codegen-units = 1
+strip = "symbols"
+
+[workspace]