fix: add --project to DiffProgramsArgs and DiffFunctionsArgs

The diff subcommands were missing --project fields, causing clap to
reject the argument when tests passed --project to diff commands.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli.rs

@@ -623,6 +623,8 @@ pub struct DiffProgramsArgs {
     pub program2: String,
     #[arg(long)]
     pub format: Option<String>,
+    #[arg(long)]
+    pub project: Option<String>,
 }
 
 #[derive(Args, Clone, Serialize, Deserialize, Debug)]
@@ -633,6 +635,8 @@ pub struct DiffFunctionsArgs {
     pub func2: String,
     #[arg(long)]
     pub format: Option<String>,
+    #[arg(long)]
+    pub project: Option<String>,
 }
 
 #[derive(Subcommand, Clone, Serialize, Deserialize, Debug)]

src/main.rs

@@ -223,6 +223,10 @@ fn extract_project_from_command(command: &Commands) -> Option<String> {
             cli::ProgramCommands::Info(args) => args.project.clone(),
             cli::ProgramCommands::Export(args) => args.project.clone(),
         },
+        Commands::Diff(cmd) => match cmd {
+            cli::DiffCommands::Programs(args) => args.project.clone(),
+            cli::DiffCommands::Functions(args) => args.project.clone(),
+        },
         Commands::Batch(args) => args.project.clone(),
         _ => None,
     }