fix(docs): Clarify content on portals (AztecProtocol#6431)

Updates info on portal contracts.

Also:
- also adds a robots.txt file 
- renames the Sandbox Reference section to Sandbox. It's already nested
under the Reference section and we had 2 pages with the same name
- Removes some duplicate info from the Sandbox Reference page
- Moves the Core Components page above the Concepts section in the top
header

closes: AztecProtocol/dev-rel#262
- There is already a good how-to in the docs. I just updated it.

docs/docs/aztec/aztec/concepts/_category_.json

@@ -1,6 +1,6 @@
 {
-    "position": 1,
-    "collapsible": true,
-    "collapsed": true,
-    "label": "Concepts"
+  "position": 2,
+  "collapsible": true,
+  "collapsed": true,
+  "label": "Concepts"
 }

docs/docs/aztec/aztec/concepts/index.md

@@ -29,7 +29,7 @@ Private state works with UTXOs, or what we call notes. To keep things private, e
 
 Public state works similarly to other chains like Ethereum, behaving like a public ledger. Public data is stored in a [public data tree](/aztec/aztec/concepts/storage/trees/index.md#public-state-tree).
 
-Aztec [smart contract](/aztec/aztec/concepts/smart_contracts/index.md) developers should keep in mind that different types are used when manipulating private or public state. Working with private state is creating commitments and nullifiers to state, whereas working with public state is directly updating state. 
+Aztec [smart contract](/aztec/aztec/concepts/smart_contracts/index.md) developers should keep in mind that different types are used when manipulating private or public state. Working with private state is creating commitments and nullifiers to state, whereas working with public state is directly updating state.
 
 ## Accounts
 
@@ -51,7 +51,7 @@ Aztec allows private communications with Ethereum - ie no-one knows where the tr
 
 This is achieved through portals - these are smart contracts deployed on an EVM that are related to the Ethereum smart contract you want to interact with.
 
-Learn more about portals [here](/aztec/aztec/concepts/smart_contracts/communication/cross_chain_calls).
+Learn more about portals [here](/protocol-specs/l1-smart-contracts/index.md).
 
 ## Circuits
 
@@ -72,4 +72,3 @@ Explore the Concepts for a deeper understanding into the components that make up
 ### Start coding
 
 Follow the [developer getting started guide](/getting_started/getting_started).
-

docs/docs/aztec/aztec/concepts/smart_contracts/communication/index.md

@@ -3,8 +3,10 @@ title: Contract Communication
 sidebar_position: 5
 ---
 
-This section will walk over communication types that behaves differently than normal function calls.
+## Private / Public execution
 
-Namely, if functions are in different domains, private vs. public, their execution behaves a little differently to what you might expect! See [Private \<--\> Public execution](./public_private_calls.md).
+See [Private \<--\> Public execution](./public_private_calls.md) for information about how Aztec contracts pass information between these execution contexts.
 
-Likewise, executing a function on a different domain than its origin needs a bit extra thought. See [L1 \<--\> L2 communication](./cross_chain_calls.md).
+## Cross-chain communication
+
+Read the protocol specification about Cross-chain communication between Aztec and Ethereum [here](../../../../../protocol-specs/l1-smart-contracts/index.md).

docs/docs/aztec/aztec/concepts/smart_contracts/functions/context.md

@@ -126,7 +126,7 @@ The public call stack contains all of the external function calls that are creat
 
 ### New L2 to L1 msgs
 
-New L2 to L1 messages contains messages that are delivered to the [l1 outbox](/aztec/aztec/concepts/smart_contracts/communication/cross_chain_calls) on the execution of each rollup.
+New L2 to L1 messages contains messages that are delivered to the [l1 outbox](/protocol-specs/l1-smart-contracts/index.md) on the execution of each rollup.
 
 ## Public Context
 

docs/docs/aztec/aztec/core_components.md

@@ -1,6 +1,6 @@
 ---
 title: Core Components
-sidebar_position: 2
+sidebar_position: 1
 ---
 
 Aztec Labs is building a layer 2 rollup on Ethereum focused on 3 things:
@@ -39,7 +39,7 @@ A user of the Aztec network will interact with the network through Aztec.js. Azt
 
 ### Private Execution Environment
 
-The PXE provides a secure environment for the execution of sensitive operations, ensuring private information and decrypted data are not accessible to unauthorized applications. It hides the details of the [state model](/aztec/aztec/concepts/state_model/index.md) from end users, but the state model is important for Aztec developers to understand as it has implications for [private/public execution](/aztec/aztec/concepts/smart_contracts/communication/public_private_calls.md) and [L1/L2 communication](/aztec/aztec/concepts/smart_contracts/communication/cross_chain_calls). The PXE also includes the [ACIR Simulator](/aztec/aztec/concepts/pxe/acir_simulator.md) for private executions and the KeyStore for secure key management.
+The PXE provides a secure environment for the execution of sensitive operations, ensuring private information and decrypted data are not accessible to unauthorized applications. It hides the details of the [state model](/aztec/aztec/concepts/state_model/index.md) from end users, but the state model is important for Aztec developers to understand as it has implications for [private/public execution](/aztec/aztec/concepts/smart_contracts/communication/public_private_calls.md) and [L1/L2 communication](../../protocol-specs/l1-smart-contracts/index.md). The PXE also includes the [ACIR Simulator](/aztec/aztec/concepts/pxe/acir_simulator.md) for private executions and the KeyStore for secure key management.
 
 Procedurally, the PXE sends results of private function execution and requests for public function executions to the [sequencer](/aztec/aztec/concepts/nodes_clients/sequencer), which will update the state of the rollup.