Pin sphinx-gp-llms to the fork that fixes the .md twin links

sphinx-gp-llms links a `.md` twin beside every generated page, including
genindex and py-modindex, which have no twin. That is four dead links in
every assembled libtmux.org build, and the last four the site had.

The fix is on the private fork's fix/md-twin-link-on-generated-pages.
Upstream gp-sphinx is public and takes no push from here, so the fork is
where it lives until a release carries it.

Three things this needed, none obvious:

- Only sphinx-gp-llms is redirected, not the gp-sphinx meta-package.
  Pinning the whole thing makes uv resolve its siblings from the fork
  too, and they are published on PyPI at a version the fork does not
  carry.
- It has to be declared as a direct dependency. It arrives transitively
  through gp-sphinx, and [tool.uv.sources] only redirects direct ones.
- gp-sphinx==0.1.0a37 pins sphinx-gp-llms==0.1.0a37 while the fork
  carries 0.1.0a38 — the fix plus its own bump — so the constraint is
  overridden. That is narrower than rewriting the fork's version to
  match a release it is ahead of.

Pinned in this worktree only. docs-site is what libtmux.org's assembly
reads; PyPI is what everyone else gets and this does not change it.

Verified by deleting .venv and re-syncing: 0.1.0a38 from git, fix
present. The previous state was a hand-patched site-packages that any
uv sync would have silently reverted.

Assembled site: 1872 pages, 403476 links checked, 0 broken.

Author: tony

pyproject.toml

@@ -53,6 +53,10 @@ Changes = "https://github.com/tmux-python/libtmux/blob/master/CHANGES"
 dev = [
   # Docs (via gp-sphinx)
   "gp-sphinx==0.1.0a37",
+  # Declared directly so [tool.uv.sources] can redirect it; it would
+  # otherwise arrive transitively through gp-sphinx, where a source override
+  # does not reach.
+  "sphinx-gp-llms",
   "sphinx-autodoc-api-style==0.1.0a37",
   "sphinx-autodoc-pytest-fixtures==0.1.0a37",
   "sphinx-autobuild",
@@ -76,6 +80,7 @@ dev = [
 
 docs = [
   "gp-sphinx==0.1.0a37",
+  "sphinx-gp-llms",
   "sphinx-autodoc-api-style==0.1.0a37",
   "sphinx-autodoc-pytest-fixtures==0.1.0a37",
   "sphinx-autobuild",
@@ -288,3 +293,28 @@ testpaths = [
 markers = [
   "integration: sphinx integration tests (require full sphinx build)",
 ]
+
+[tool.uv.sources]
+# sphinx-gp-llms from the private fork, for the one fix libtmux.org needs.
+#
+# sphinx-gp-llms links a `.md` twin beside every page, including `genindex`
+# and `py-modindex`, which have no twin — four dead links in the assembled
+# site with nothing upstream to point at yet. The fix is on
+# `fix/md-twin-link-on-generated-pages`; upstream is public and takes no
+# push from here, so it lives on the private fork until a release carries it.
+#
+# Only this one sub-package is redirected, not the `gp-sphinx` meta-package:
+# pinning the whole thing makes uv resolve its siblings from the fork too, and
+# they are published on PyPI at a pinned version the fork does not carry.
+#
+# Pinned in this worktree only. `docs-site` is what libtmux.org's assembly
+# reads; the published package on PyPI is what everyone else gets, and this
+# does not change that.
+sphinx-gp-llms = { git = "ssh://git@github.com/tony/gp-sphinx.git", branch = "fix/md-twin-link-on-generated-pages", subdirectory = "packages/sphinx-gp-llms" }
+
+[tool.uv]
+# `gp-sphinx==0.1.0a37` pins `sphinx-gp-llms==0.1.0a37`, and the fork carries
+# 0.1.0a38 — the fix plus its own version bump. Overriding the constraint is
+# narrower than rewriting the fork's version to match a release it is ahead
+# of, and it is the only pin standing between this build and four dead links.
+override-dependencies = ["sphinx-gp-llms"]