fix(author): correct LUT prefix nesting in jinja command

[Acuspeedster]

Types of changes

• Hot fix (emergency fix and release)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation (change which affects the documentation site)
• Breaking change (fix or feature that would cause existing functionality to change)
• Release (develop -> main)

Quality assurance (all should be covered).

• My code follows the code style of this project.
• Documentation for my change is up to date?
• My PR meets testing requirements.
• All new and existing tests passed.
• All commits are signed-off.

Summary

Fix trestle author jinja lookup-table prefix wrapping (-elp/--external-lut-prefix) to match documented behavior.

Problem:

• JinjaCmd.load_LUT() previously mutated the LUT in-place and created self-referential structures when a prefix was provided.
• This could cause unexpected template variable resolution and did not correctly enforce nested prefix wrapping as documented.

Fix:

• Read LUT file using a context manager.
• Build nested prefix wrappers deterministically (e.g., fruit.tropical -> {'fruit': {'tropical': <lut>}}).

Tests:

• Added regression test for prefix nesting behavior.
• Updated existing lookup-table test to validate unprefixed LUT behavior without passing -elp.

Files changed:

• trestle/core/commands/author/jinja.py
• tests/trestle/core/commands/author/jinja_cmd_test.py

Targeted validation run:

• pytest tests/trestle/core/commands/author/jinja_cmd_test.py::test_jinja_lookup_table tests/trestle/core/commands/author/jinja_cmd_test.py::test_jinja_lookup_table_prefix_nesting -q --basetemp .pytest_tmp
• Result: 2 passed

Key links:

• Sonar coverage

Before you merge

• Ensure it is a 'squash commit' if not a release.
• Ensure CI is currently passing
• Check sonar. If you are working for a fork a maintainer will reach out, if required.

[degenaro]

@butler54 Please review.