Feat/missing relation requirements

[claudiiolima]

Description

This PR adds support for running StrictDoc on subprojects that intentionally do not contain all cross-project relations.

Our project is split into hardware, mechanical, and firmware repositories. At system-repo level, all requirement relations resolve correctly. At subproject level, some parent/child links point to requirements that exist only in another repository. Today, this blocks useful workflows such as:

1. Building firmware-only docs with full local traceability.
2. Building docs in CI even when external repos are not cloned.
3. Including source traceability in a subproject without pulling the full system context.

Problem

StrictDoc currently raises an exception when a referenced relation is missing, which stops export/server flows and breaks subproject-level documentation builds.

Solution

Introduce a new relaxed mode that allows builds to continue when requirement relations are missing.

In this mode, StrictDoc:

1. Continues building instead of failing.
2. Emits warnings about unresolved relations.
3. Highlights missing relations in rendered outputs.
4. Tracks and exposes missing-relations statistics.
5. Supports searching/filtering for requirements with missing relations.

CLI / Config

Added relation-scoped option:

1. --allow-missing-relation-requirements

Compatibility:

1. Legacy parent-only naming is still accepted for backward compatibility.

User-visible behavior

When relaxed mode is enabled:

1. Missing parent and missing child relations are tolerated.
2. Warnings are shown in document-level outputs.
3. A project-level warning is shown on the index page.
4. Missing relations are visually highlighted in requirement relation sections.
5. Project statistics include a metric for requirements with missing relations.

Notes

This change is designed for multi-repo/subproject workflows where some upstream/downstream requirement links are expected to be unavailable in the current checkout.

[claudiiolima]

Some images

Index page

Metrics Page

Requirement Page

[claudiiolima]

I still have to implement missing file conditions.

[stanislaw]

Hey @claudiiolima thanks a lot for starting this! @mettta and I discussed and created this ticket recently, and it is very close to what you are doing in your PR: #2937.

One thing that we were planning to do was to re-use the engine of Validations: https://strictdoc.readthedocs.io/en/stable/stable/docs/strictdoc_01_user_guide.html#18.1-Custom-validations.

                    # Attach a validation issue to the entire node.
                    traceability.validation_index.add_issue(
                        node,
                        issue="The whole node is really bad.",
                        field=None,
                        subject=f"Node: {node.reserved_title}",
                    )

Give us some time to get through the epic #2964 and some other open issues raised by several users. I hope I can get to reviewing your PR in detail within the next few days.

[claudiiolima]

@stanislaw Thanks for the initial review!

I've made some changes since then, including leveraging issues from validation_index. I also implemented missing-file warnings and rendering support, and added the same rendering functionality to the table view.

[claudiiolima]

There is still an uncovered case: the relationship between a source file and a requirement has not been implemented yet.

[bartekpaczek]

Does the change cover only PARENT/CHILD relation or also just [LINK:] to UID or ANCHOR? It would be great if that could also cover it.

[claudiiolima]

Does the change cover only PARENT/CHILD relation or also just [LINK:] to UID or ANCHOR? It would be great if that could also cover it.

For now I only have worked at PARENT/CHILD/FILE relations. But LINK and ANCHOR could be added too.

[stanislaw]

FYI: Reviewing and integrating this is on my list for the next few days.