fix: doc rendering issue

.github/workflows/book.yml

@@ -3,7 +3,7 @@ name: AirScript book
 on:
   push:
     branches:
-      - main
+      - next
 
 jobs:
   deploy:

docs/src/description/syntax.md

@@ -6,7 +6,7 @@ This page specifies the basic syntax, types, and keywords of AirScript.
 
 AirScript defines the following keywords:
 
-- `$rand`: used to access random values provided by the verifier.
+- `\$rand`: used to access random values provided by the verifier.
 - `def`: used to [define the name](./structure.md) of an AirScript module.
 - `boundary_constraints`: used to declare the [source section](./structure.md#source-sections) where the [boundary constraints are described](./constraints.md#boundary_constraints).
   - `first`: used to access the value of a trace column at the first row of the trace. _It may only be used when defining boundary constraints._
@@ -21,13 +21,13 @@ AirScript defines the following keywords:
 
 ## Built-in variables
 
-Built-in variables are identified by the starting character `$`.
+Built-in variables are identified by the starting character `\$`.
 
-### $rand
+### \$rand
 
-Currently, the only built-in is `$rand`, which is used to get random values provided by the verifier.
+Currently, the only built-in is `\$rand`, which is used to get random values provided by the verifier.
 
-These random values may be accessed by using the indexing operator on `$rand`. For example, `$rand[i]` provides the `ith` random value.
+These random values may be accessed by using the indexing operator on `\$rand`. For example, `\$rand[i]` provides the `ith` random value.
 
 Random values may only be accessed within source sections for constraints, i.e. the [`boundary_constraints` section](./constraints.md#boundary-constraints-boundary_constraints) and the [`transition_constraints` section](./constraints.md#transition-constraints-transition_constraints).
 
@@ -37,7 +37,7 @@ Random values may only be accessed within source sections for constraints, i.e.
 - `.` is used to access a boundary on a trace column, e.g. `a.first` or `a.last`
 - `[` and `]` are used for defining arrays in [type declarations](./declarations.md) and for indexing in [constraint descriptions](./constraints.md)
 - `,` is used as a delimiter for defining arrays in [type declarations](./declarations.md)
-- `$` is used to indicate a special built-in value. Currently, it is only used with `$rand` for accessing random values.
+- `\$` is used to indicate a special built-in value. Currently, it is only used with `\$rand` for accessing random values.
 
 ## Identifiers
 
@@ -88,7 +88,7 @@ These accessors may only be used in the specified [source section](./structure.m
 The following accessors may only be applied to trace columns when they are in boundary constraint definitions.
 
 - First boundary (`.first`): accesses the trace column's value in the first row. It is only supported in [boundary constraint descriptions](./constraints.md#boundary_constraints)
-- Last boundary (`.last`): accesses the trace column's value in the first row. It is only supported in [boundary constraint descriptions](./constraints.md#boundary_constraints)
+- Last boundary (`.last`): accesses the trace column's value in the last row. It is only supported in [boundary constraint descriptions](./constraints.md#boundary_constraints)
 
 The following accessor may only be applied to public inputs declared in `public_inputs` when they are referenced in boundary constraint definitions.