Split the pagx convert command into import and export

.codebuddy/skills/pagx/SKILL.md

@@ -5,7 +5,7 @@ description: >-
   ones for size and rendering performance. Use when user asks to create, write, or
   design PAGX content, optimize or simplify a .pagx file, review PAGX structure, run
   pagx CLI commands (render, validate, format, optimize, bounds, font info/embed,
-  convert), or look up PAGX element attributes and syntax.
+  import, export), or look up PAGX element attributes and syntax.
 ---
 
 # PAGX Skill
@@ -44,4 +44,4 @@ generation or optimization task.
 | `spec-essentials.md` | Node types, Layer rendering pipeline, painter scope, text system, masking, resources |
 | `design-patterns.md` | Structure decisions (Layer vs Group), text layout patterns, practical pitfall patterns |
 | `attributes.md` | Attribute defaults, enumerations, required attributes |
-| `cli.md` | CLI commands — `render`, `validate`, `optimize`, `format`, `bounds`, `font info`, `font embed`, `convert` |
+| `cli.md` | CLI commands — `render`, `validate`, `optimize`, `format`, `bounds`, `font info`, `font embed`, `import`, `export` |

.codebuddy/skills/pagx/references/cli.md

@@ -220,32 +220,52 @@ primary font. System fallback fonts are always appended after user-specified fal
 
 ---
 
-## pagx convert
+## pagx import
 
-Convert between PAGX and other formats. The conversion direction is inferred from file
-extensions (e.g., `.pagx` → `.svg` or `.svg` → `.pagx`). Loads the input, converts the
-document, and writes the result. Import warnings are printed but do not prevent conversion.
+Import a file from another format (e.g. SVG) and convert it to PAGX. The input format is
+inferred from the file extension unless `--format` is specified. Import warnings are printed
+but do not prevent conversion.
 
 ```bash
-pagx convert input.pagx output.svg                   # PAGX to SVG
-pagx convert input.svg output.pagx                   # SVG to PAGX
-pagx convert --indent 4 input.pagx output.svg        # PAGX to SVG with 4-space indent
-pagx convert --no-xml-declaration input.pagx out.svg
-pagx convert --no-convert-text-to-path input.pagx out.svg  # keep <text> elements
-pagx convert --format svg input.pagx output               # specify SVG output format
-pagx convert --no-expand-use input.svg output.pagx   # SVG to PAGX without expanding <use>
+pagx import --input icon.svg                     # SVG to icon.pagx
+pagx import --input icon.svg --output out.pagx   # SVG to out.pagx
+pagx import --format svg --input drawing.xml     # force SVG format
 ```
 
 | Option | Description |
 |--------|-------------|
-| `--format <format>` | Override output format (`svg`, `pagx`; default: inferred from output extension) |
-| `--indent <n>` | SVG indentation spaces (default: 2, valid range: 0–16) |
-| `--no-xml-declaration` | Omit the `<?xml ...?>` declaration (SVG output only) |
-| `--no-convert-text-to-path` | Keep text as `<text>` elements instead of converting to `<path>` (SVG output only) |
-| `--no-expand-use` | Do not expand `<use>` references (SVG input only) |
-| `--flatten-transforms` | Flatten nested transforms into single matrices (SVG input only) |
-| `--preserve-unknown` | Preserve unsupported SVG elements as Unknown nodes (SVG input only) |
-
-The command takes two positional arguments: `<input>` and `<output>`. Use `--format` when the
-output extension does not make the format unambiguous. On success the command prints
-`pagx convert: wrote <path>` and exits 0; on failure it prints an error and exits 1.
+| `--input <file>` | Input file to import (required) |
+| `--output <file>` | Output PAGX file (default: `<input>.pagx`) |
+| `--format <format>` | Force input format (`svg`; default: inferred from input extension) |
+| `--svg-no-expand-use` | Do not expand `<use>` references |
+| `--svg-flatten-transforms` | Flatten nested transforms into single matrices |
+| `--svg-preserve-unknown` | Preserve unsupported SVG elements as Unknown nodes |
+
+On success the command prints `pagx import: wrote <path>` and exits 0; on failure it prints
+an error and exits 1.
+
+---
+
+## pagx export
+
+Export a PAGX file to another format (e.g. SVG). The output format is inferred from the
+output file extension, or defaults to SVG if no output is specified.
+
+```bash
+pagx export --input icon.pagx                    # PAGX to icon.svg
+pagx export --input icon.pagx --output out.svg   # PAGX to out.svg
+pagx export --format svg --input icon.pagx       # force SVG format
+pagx export --input icon.pagx --svg-indent 4     # 4-space indent
+```
+
+| Option | Description |
+|--------|-------------|
+| `--input <file>` | Input PAGX file (required) |
+| `--output <file>` | Output file (default: `<input>.<format>`) |
+| `--format <format>` | Force output format (`svg`; default: inferred from output extension or `svg`) |
+| `--svg-indent <n>` | Indentation spaces (default: 2, valid range: 0–16) |
+| `--svg-no-xml-declaration` | Omit the `<?xml ...?>` declaration |
+| `--svg-no-convert-text-to-path` | Keep text as `<text>` elements instead of `<path>` |
+
+On success the command prints `pagx export: wrote <path>` and exits 0; on failure it prints
+an error and exits 1.

src/cli/CliUtils.h

@@ -97,6 +97,29 @@ inline std::shared_ptr<tgfx::Typeface> ResolveFallbackTypeface(const std::string
   return ResolveSystemTypeface(family, style);
 }
 
+/**
+ * Extracts the file extension from a path (without the dot), or returns an empty string if none.
+ */
+inline std::string GetFileExtension(const std::string& path) {
+  auto dot = path.rfind('.');
+  if (dot != std::string::npos) {
+    return path.substr(dot + 1);
+  }
+  return {};
+}
+
+/**
+ * Replaces the file extension in a path with a new extension. If the path has no extension, appends
+ * the new extension.
+ */
+inline std::string ReplaceExtension(const std::string& path, const std::string& newExt) {
+  auto dot = path.rfind('.');
+  if (dot != std::string::npos) {
+    return path.substr(0, dot + 1) + newExt;
+  }
+  return path + "." + newExt;
+}
+
 inline std::string EscapeJson(const std::string& input) {
   std::string result = {};
   result.reserve(input.size() + 16);