PDF: const-qualify by-value scalar params in definitions

Align pdf_page_extractor and pdf_document_parser with the module's
prevailing convention (const on by-value scalar definition params).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uqx1dUpDUykRxui8FYwxvM

Author: andiwand

src/odr/internal/pdf/pdf_document_parser.cpp

@@ -528,7 +528,7 @@ Resources *parse_resources(State &state, const Object &object);
 /// Read an integer image-dictionary entry (e.g. `/Width`), resolving an
 /// indirect reference, defaulting to `fallback`.
 std::int32_t image_int(DocumentParser &parser, const Dictionary &dictionary,
-                       const std::string &key, std::int32_t fallback) {
+                       const std::string &key, const std::int32_t fallback) {
   return static_cast<std::int32_t>(
       parser.resolve_object_copy(dictionary.get(key))
           .as_integer_opt()
@@ -557,9 +557,9 @@ std::vector<double> image_decode(DocumentParser &parser,
 /// the base image stays opaque.
 std::vector<std::uint8_t> resolve_mask_alpha(DocumentParser &parser,
                                              const Object &mask,
-                                             std::int32_t base_width,
-                                             std::int32_t base_height,
-                                             bool stencil) {
+                                             const std::int32_t base_width,
+                                             const std::int32_t base_height,
+                                             const bool stencil) {
   if (!mask.is_reference()) {
     return {};
   }

src/odr/internal/pdf/pdf_page_extractor.cpp

@@ -39,7 +39,7 @@ Font *lookup_font(const Resources &resources, const std::string &name,
 /// diacritic block (0x18–0x1F), the typographic block (0x80–0x9E), and the
 /// euro (0xA0) need overriding; every other byte stands for the code point of
 /// the same value. The few undefined slots (0x7F, 0x9F, 0xAD) pass through.
-char32_t pdf_doc_encoding_to_unicode(std::uint8_t byte) {
+char32_t pdf_doc_encoding_to_unicode(const std::uint8_t byte) {
   switch (byte) {
   case 0x18:
     return U'˘'; // breve
@@ -404,8 +404,9 @@ std::array<double, 3> color_to_rgb(const GraphicsState::Color &color) {
 /// Emit a path-painting element from the path accumulated in `state` and the
 /// current paint state, then clear the path (as every painting operator does).
 /// `close` first closes the current subpath (the `s`/`b`/`b*` variants).
-void paint_path(std::vector<PageElement> &out, GraphicsState &state, bool fill,
-                bool stroke, bool even_odd, bool close) {
+void paint_path(std::vector<PageElement> &out, GraphicsState &state,
+                const bool fill, const bool stroke, const bool even_odd,
+                const bool close) {
   if (close) {
     state.path_close();
   }