Make copier input robust against bad project names

Also reduce length of validation message as copier's statusline
provided by the prompt_toolkit is limited to one line.

Author: dalito

CHANGELOG.md

@@ -61,7 +61,10 @@ The format is inspired by [Keep a Changelog](https://keepachangelog.com/en/1.1.0
 - `just gen-project` tolerates a missing `project/` directory. #161
 - Generated YAML files (GitHub Actions, mkdocs) and `test_data.py` now pass
   default yamllint/ruff checks. #170
-- `just _update-linkml` uses `uv lock` instead of `uv add` to avoid side-effect of adding linkml as main dependency. #159
+- Reject invalid `project_name` input (e.g. trailing dot, single character) at
+  the prompt with a friendly message instead of crashing later.
+- `just _update-linkml` uses `uv lock` instead of `uv add` to avoid side-effect
+  of adding linkml as main dependency. #159
 - Force-push to `gh-pages` during docs deployment to avoid history conflicts. #154
 - Align `uv sync` invocation in template workflows. #150
 - Skip ShEx integration test on Python 3.13 and install dependencies in the
@@ -145,7 +148,7 @@ The format is inspired by [Keep a Changelog](https://keepachangelog.com/en/1.1.0
 ### Added
 
 - New pre-commit command that updates the uv.lock file. #81
-- Automatic publishing of releases to Zenodo ([doi:10.5281/zenodo.15163584](https://doi.org/10.5281/zenodo.15163584)). #
+- Automatic publishing of releases to Zenodo ([doi:10.5281/zenodo.15163584](https://doi.org/10.5281/zenodo.15163584)).
 
 ### Fixed
 

copier.yaml

@@ -9,6 +9,12 @@ project_name:
   type: str
   help: What is your project name?
   default: my-awesome-schema
+  # Catch invalid input and show a friendly message.
+  validator: >-
+    {% if not (project_name | regex_search('^[A-Za-z][A-Za-z0-9 _\-]*[A-Za-z0-9]$',
+       ignorecase=False)) %}
+    Use 2+ of letters, digits, space, '-', '_'; start with letter, end alnum.
+    {% endif %}
 
 project_slug:
   type: str
@@ -22,8 +28,7 @@ project_slug:
   validator: >-
     {% if not (project_slug | regex_search('^[a-z][_a-z0-9\-]+$',
        ignorecase=False)) %}
-    project_slug must start with a lowercase letter, followed by lowercase
-    letters, digits, dashes or underscores.
+    Start with a lowercase letter, then lowercase letters, digits, '-' or '_'.
     {% endif %}
 
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