Pin copier for breaking change and more uniformly across install methods

A recent upstream change in copier[1] brings some interesting
functionality we may want to use at some point, but currently breaks our
`NavaWorker`/`src_exclude` support by changing the return type of
`_render_path()`/how its return value is handled. So pin to right before
that change for now.

Also, by moving the pinning out of `tool.uv.sources`, the same version
should be utilized whether installed via pipx or uv, which was not the
case before. `pipx` was using the latest release on PyPI (v9.4.1) and
`uv tool install` was fetching an even newer
version (`9.4.1.post70.dev0+f4ba854`) than the one in the lock file,
since it doesn't yet support a `--locked` flag (or similar).

[1] copier-org/copier@557c0d6

pyproject.toml

@@ -14,7 +14,12 @@ readme = "README.md"
 requires-python = ">=3.11"
 dependencies = [
     "click>=8.1.7",
-    "copier",
+    # Pin to just before
+    #
+    # https://github.com/copier-org/copier/commit/557c0d614497e9b1b3382d4fd4be0d773d612bff
+    #
+    # as that change breaks our `NavaWorker`/src_exclude setup.
+    "copier@git+https://github.com/copier-org/copier@cdbd0b14e688d04a95873513473bf14e58784171",
     "packaging>=24.1",
     "platformdirs>=4.3.6",
     "pyyaml>=6.0.2",
@@ -27,9 +32,6 @@ dependencies = [
 [tool.uv]
 required-version = ">0.5.8"
 
-[tool.uv.sources]
-copier = { git = "https://github.com/copier-org/copier" }
-
 [project.scripts]
 nava-platform = "nava.platform.cli.__main__:__main__"
 
@@ -107,6 +109,9 @@ convention = "google"
 [tool.hatch.build.targets.wheel]
 packages = ["nava"]
 
+[tool.hatch.metadata]
+allow-direct-references = true
+
 [build-system]
 requires = ["hatchling"]
 build-backend = "hatchling.build"