make spec infra more ergonomic

Signed-off-by: Onur Özkan <work@onurozkan.dev>

README.md

@@ -2,7 +2,7 @@
 
 Kaptan is a modular flight controller platform focused on deterministic bare-metal execution for flight-critical paths and strong verification discipline around the rest of the stack.
 
-The repository is currently in infrastructure setup. Formal project specifications should be linked directly from the code they govern through compile-time attributes.
+The repository is currently in infrastructure setup. Formal project specifications are automatically checked beside the file-backed modules they govern.
 
 ## Current Direction
 
@@ -32,14 +32,14 @@ Formal specs should be colocated with the code or board package they govern.
 - Version history should live inside the same spec file as additional spec entries, not in the filename.
 - Each appended spec entry should begin with version marker such as `# --- version: 0.1.0 ---`.
 - Inside a spec entry, `#` is reserved for version markers and content headings should start at `##`.
-- Rust items should link to those sidecar specs through `#[spec("...")]`.
-- Missing linked spec files must fail compilation.
+- Each file-backed Rust module requires a same-name `.spec.md` sidecar.
+- Modules that intentionally have no formal specification must declare `no_spec!("reason");` at module scope.
+- Missing sidecars and modules that have both a sidecar and `no_spec!(...)` fail the build.
 
 Example:
 
 ```rust
-use kaptan_spec::spec;
+use kaptan_spec::no_spec;
 
-#[spec("control_loop.spec.md")]
-pub struct ControlLoop;
+no_spec!("Crate root declares child modules only.");
 ```