Rename model guide to usage

README.md

@@ -130,7 +130,7 @@ output. It only owns the immutable, presentation-neutral data model passed betwe
 
 - [Installation](docs/installation.md): install the development package and verify it.
 - [Getting started](docs/getting-started.md): create a snippet and inspect a selected line.
-- [Model](docs/model.md): work with snippets, lines, annotations, segments, and transformations.
+- [Usage](docs/usage.md): work with snippets, lines, annotations, segments, and transformations.
 - [Documentation index](docs/index.md): read the package overview and boundaries.
 
 ## Contributing

docs/getting-started.md

@@ -38,4 +38,4 @@ index=3 number=26 selected=true
 
 `selectLines()` uses one-based positions inside the snippet. Selection marks a
 line; it does not remove the other lines or define a visual effect. Continue
-with the [model](model.md) to annotate, slice, indent, and export snippets.
+with the [usage guide](usage.md) to annotate, slice, indent, and export snippets.

docs/index.md

@@ -17,7 +17,7 @@ echo $snippet->lines()[2]->number; // 26
 
 - [Installation](installation.md): install the package and verify it can create a snippet.
 - [Getting started](getting-started.md): create a snippet and inspect a selected line.
-- [Model](model.md): work with snippets, lines, annotations, segments, and transformations.
+- [Usage](usage.md): work with snippets, lines, annotations, segments, and transformations.
 
 The package owns the portable snippet model. It does not read files, detect
 languages, locate declarations, tokenize code, or render output.

docs/model.md → docs/usage.md

@@ -1,4 +1,4 @@
-# Model
+# Usage
 
 Code Snippet represents source text and presentation hints with four immutable
 values. Transformations return a new value, so the original snippet remains