docs: write README links absolute so they resolve on PyPI

AGENTS.md

@@ -29,9 +29,12 @@ non-Provider attributes that exist to exercise the skip path.
 
 Real work **not scheduled** becomes a GitHub issue.
 
+Every link in `README.md` must be absolute: `https://github.com/modern-python/<repo>/blob/main/<path>`,
+or `.../tree/main/<path>` for a directory. Never a relative path: `README.md` is also the PyPI long
+description, and PyPI does not rewrite relative links, so a relative one 404s on the package page.
+
 An invariant is a test whose name is the claim, with a docstring opening `INVARIANT:` and a second
 paragraph naming **what breaks it** — design rationale, not a report of what this one test catches.
-Nothing enforces that docstring shape; it is read at review time.
 
 ## Agent skills
 

README.md

@@ -140,7 +140,7 @@ introspection cannot identify the caller.
 
 ## 📦 [PyPI](https://pypi.org/project/modern-di-pytest)
 
-## 📝 [License](LICENSE)
+## 📝 [License](https://github.com/modern-python/modern-di-pytest/blob/main/LICENSE)
 
 ## Part of `modern-python`