Bake task macros

Procedural macros for socketry-bake. Most users access the attribute through #[bake::task], re-exported by the core library.

The attribute preserves the original synchronous function and generates a sibling function_task() returning a task descriptor. It also adds the descriptor to Bake's link-time registration table for Registry::discover(). Nested Rust modules become task namespaces. Use name = "namespace:task" to override the command name, and runtime = ::alias if the core dependency was renamed from bake.

Use #[bake::task(output)] when a task handles its own user-facing output. Use #[bake(input)] input: bake::Value to receive the result from the preceding task.

Tasks accept owned FromStr arguments and an optional context reference. They return a Result with a serializable successful value and a displayable error. The macro rejects async, unsafe, foreign, generic, variadic, and receiver-based signatures.

See the workspace documentation for examples.