fix: remove copier from generated project dev dependencies

copier should be invoked via `uvx copier` rather than installed as a
dev dependency of generated projects. Update docs accordingly.

Closes #343

Author: claude

.github/CONTRIBUTING.md

@@ -20,7 +20,7 @@ The template has tests for:
 However, this does not test whether processes like CI and docs work correctly. You can ensure that these are checked by:
 
 - Making your changes on a branch of <https://github.com/DiamondLightSource/python-copier-template>
-- Running `copier update --vcs-ref=<branch_name>` in the repo where you would like to demonstrate the behaviour
+- Running `uvx copier update --vcs-ref=<branch_name>` in the repo where you would like to demonstrate the behaviour
 - Linking to that demonstration repo in the PR
 
 ## Developer Information

docs/how-to/update-template.md

@@ -5,7 +5,7 @@
 To track changes to the upstream template, run
 
 ```
-copier update
+uvx copier update
 ```
 
 This will fetch the latest tagged release of the template, and apply any changes to your working copy. It will prompt for answers again, giving your previous answers as the defaults.
@@ -32,7 +32,7 @@ The following steps are recommended to update your project, especially for infre
 - fix issues found by the above
 - commit the changes
 - update the template
-    - `copier update`
+    - `uvx copier update`
 - fix any merge conflicts
 - validate that the project still works
     - `tox -p`

template/pyproject.toml.jinja

@@ -21,7 +21,6 @@ requires-python = ">=3.11"
 
 [dependency-groups]
 dev = [
-    "copier",
     {% if type_checker=="mypy" %}"mypy",
     {% endif %}{% if sphinx %}"myst-parser",
     {% endif %}"pre-commit",