docs: remove all stale JSON protocol references

Update all documentation to reflect protobuf-only protocol format.
State data (state.json) references are unchanged — only protocol
format references updated.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: mohamedmansour

DESIGN.md

@@ -173,7 +173,7 @@ pub struct Predicate {
 ```
 #### Serialization Requirements
 - Protobuf binary serialization/deserialization as the primary format, using `prost` for zero-copy decoding
-- JSON serialization/deserialization supported for backward compatibility
+- JSON output supported via `webui inspect` for debugging only
 - Support for custom error types and propagation
 - Validation of protocol structure during deserialization
 - Performance optimizations for large protocol structures

README.md

@@ -56,7 +56,7 @@ cargo build --release
 The `webui` CLI builds your app folder into the WebUI protocol format:
 
 ```bash
-# Build an app (outputs protocol.json and component CSS to the out folder)
+# Build an app (outputs protocol.bin and component CSS to the out folder)
 cargo run -p webui-cli -- build ./my-app --out ./dist
 
 # Specify a custom entry file

docs/guide/advanced/protocol.md

@@ -43,6 +43,6 @@ The `If` fragment uses a `Condition` oneof to express its predicate:
 | `Compound` | Logical AND/OR of two nested conditions |
 | `Identifier` | Direct reference to a state identifier |
 
-## JSON Compatibility
+## Debugging
 
-JSON serialization is still supported for backward compatibility and debugging. Use the JSON representation when inspecting protocol output manually or integrating with tools that do not support protobuf.
+Use `webui inspect` to convert protocol.bin to JSON for debugging purposes.

docs/guide/concepts/directives/index.md

@@ -19,4 +19,4 @@ WebUI directives are processed by the WebUI parser and transformed into a platfo
 Template with directives → WebUI Protocol → Native HTML output
 ```
 
-The WebUI protocol is a simple JSON structure that can be processed by any language with JSON support, making it ideal for cross-platform applications.
+The WebUI protocol is a protobuf binary structure defined by a cross-language .proto schema, making it ideal for cross-platform applications.

docs/guide/concepts/handlers/index.md

@@ -12,7 +12,7 @@ WebUI provides official handlers for several popular programming languages (othe
 
 All WebUI handlers follow the same pattern:
 
-1. They accept a WebUI protocol object (usually parsed from JSON)
+1. They accept a WebUI protocol object (parsed from protobuf binary)
 2. They process the protocol with the provided state data
 3. They render the final HTML output by evaluating directives and inserting dynamic content
 

docs/guide/concepts/handlers/rust.md

@@ -17,7 +17,7 @@ webui-state = "0.1.0"
 ## Basic Usage
 
 ```rust
-use std::fs::File;
+use webui_protocol::WebUIProtocol;
 use serde_json::{json, Value};
 use webui_handler::{handle, ResponseWriter, Result};
 use webui_protocol::WebUIProtocol;
@@ -47,8 +47,7 @@ impl ResponseWriter for StringWriter {
 
 fn main() -> Result<()> {
     // Load protocol from file
-    let protocol_file = File::open("template.json")?;
-    let protocol = WebUIProtocol::from_reader(protocol_file)?;
+    let protocol = WebUIProtocol::from_protobuf_file("template.bin")?;
 
     // Create state data
     let state = json!({

docs/tutorials/hello-world.md

@@ -87,7 +87,7 @@ Let's create a Rust application to render this template:
 ```rust
 use std::fs;
 use serde_json::Value;
-use webui_parser::{WebUIParser, Result};
+use webui_protocol::{WebUIProtocol, Result};
 use webui_handler::{handle, ResponseWriter};
 
 struct FileWriter {
@@ -120,9 +120,8 @@ impl ResponseWriter for FileWriter {
 }
 
 fn main() -> Result<()> {
-    // Parse the template at build step, then protocol will be only needed.
-    let parser = WebUIParser::new();
-    let protocol = parser.parse("src/templates/index.html", &["src/templates"])?;
+    // Load the protocol from protobuf binary
+    let protocol = WebUIProtocol::from_protobuf_file("protocol.bin")?;
 
     // Load the state
     let state_json = fs::read_to_string("state.json")?;

docs/tutorials/todo-app.md

@@ -204,7 +204,7 @@ fn main() {
     let current_state = get_state(&store);
 
     // 2. Load the protocol
-    let protocol = load_protocol("path/to/compiled/protocol.json");
+    let protocol = load_protobuf("path/to/compiled/protocol.bin");
 
     // 3. Handle the request and write to response
     handler(protocol, current_state, |chunk| {