fix: resolve unresolved [frame] intra-doc links in reference_docs

Replace link reference syntax ([FRAME](frame) with [frame]: definition)
with direct full paths (crate::pezkuwi_sdk::frame_runtime) to resolve
rustdoc link resolution issues across module boundaries.

The link definitions in //! module-level docs weren't being resolved
for /// item-level doc comments, causing "unresolved link to 'frame'"
errors in build-rustdoc CI job.

docs/sdk/src/reference_docs/runtime_vs_smart_contract.rs

@@ -19,7 +19,7 @@
 //!
 //! #### Smart Contracts in Bizinikiwi
 //! Smart Contracts are autonomous, programmable constructs deployed on the blockchain.
-//! In [FRAME](frame), Smart Contracts infrastructure is implemented by the
+//! In [FRAME](crate::pezkuwi_sdk::frame_runtime), Smart Contracts infrastructure is implemented by the
 //! [`pezpallet_contracts`] for WASM-based contracts or the
 //! [`pezpallet_evm`](https://github.com/polkadot-evm/frontier/tree/master/frame/evm) for EVM-compatible contracts. These pallets
 //! enable Smart Contract developers to build applications and systems on top of a Bizinikiwi-based
@@ -208,4 +208,3 @@
 //!   execution is crucial. Efficiently written contracts save costs and are less likely to hit gas
 //!   limits, ensuring smoother execution on the blockchain.
 //!
-//! [frame]: crate::pezkuwi_sdk::frame_runtime