fix(config[source_branch]): Change source_branch default from "master" to "main"

why: Repo default branch is main; "master" default caused broken "Edit on GitHub"
and "View source" links on every docs page.
what:
- Change source_branch parameter default in merge_sphinx_config() to "main"
- Change DEFAULT_THEME_OPTIONS["source_branch"] seed value to "main"
- Update docs/conf.py source_branch kwarg to "main"
- Update configuration.md table rows to reflect new defaults

Author: tony

docs/conf.py

@@ -33,7 +33,7 @@
     copyright=gp_sphinx.__copyright__,
     source_repository=f"{gp_sphinx.__github__}/",
     docs_url=gp_sphinx.__docs__,
-    source_branch="master",
+    source_branch="main",
     extra_extensions=[
         "package_reference",
         "sphinx_autodoc_pytest_fixtures",

docs/configuration.md

@@ -38,7 +38,7 @@ All parameters are keyword-only.
 | `remove_extensions` | `list[str] \| None` | `None` | Extensions removed from the selected base list |
 | `theme_options` | `dict[str, Any] \| None` | `None` | Deep-merged into `DEFAULT_THEME_OPTIONS` after auto-populated source/logo values |
 | `source_repository` | `str \| None` | `None` | GitHub repository URL used for issue links, footer icon URLs, and theme source metadata |
-| `source_branch` | `str` | `"master"` | Source branch stored in `html_theme_options["source_branch"]` |
+| `source_branch` | `str` | `"main"` | Source branch stored in `html_theme_options["source_branch"]` |
 | `light_logo` | `str \| None` | `None` | Light-mode logo path merged into theme options |
 | `dark_logo` | `str \| None` | `None` | Dark-mode logo path merged into theme options |
 | `docs_url` | `str \| None` | `None` | Canonical docs URL used to derive Open Graph settings |
@@ -112,7 +112,7 @@ These are injected even though they are not exposed as `DEFAULT_*` constants:
 | Constant | Value |
 | --- | --- |
 | `DEFAULT_THEME` | `"sphinx-gptheme"` |
-| `DEFAULT_THEME_OPTIONS` | footer GitHub icon, `source_repository=""`, `source_branch="master"`, `source_directory="docs/"` |
+| `DEFAULT_THEME_OPTIONS` | footer GitHub icon, `source_repository=""`, `source_branch="main"`, `source_directory="docs/"` |
 
 ### Font defaults
 

packages/gp-sphinx/src/gp_sphinx/config.py

@@ -214,7 +214,7 @@ def merge_sphinx_config(
     remove_extensions: list[str] | None = None,
     theme_options: dict[str, t.Any] | None = None,
     source_repository: str | None = None,
-    source_branch: str = "master",
+    source_branch: str = "main",
     light_logo: str | None = None,
     dark_logo: str | None = None,
     docs_url: str | None = None,

packages/gp-sphinx/src/gp_sphinx/defaults.py

@@ -115,7 +115,7 @@ class FontConfig(_FontConfigRequired, total=False):
         },
     ],
     "source_repository": "",
-    "source_branch": "master",
+    "source_branch": "main",
     "source_directory": "docs/",
 }
 """Default Furo theme options.