Improve empty-state messaging in Explorer graph views

[MuttleyD]

Context

Explorer is the graph-native visibility surface for MIDAS. It helps users inspect context, authority, evidence, drift, and runtime governance structure.

Some Explorer views can appear empty when there is no data, when data has not loaded yet, or when a filter/search returns no results. For first-time users, unclear empty states make it harder to understand whether something is broken, still loading, or simply has no records yet.

This is a low-risk frontend improvement suitable for a first-time contributor.

Scope

Improve empty-state messaging in Explorer graph and catalogue views.

Focus on places where the UI currently shows an empty panel, generic message, or unclear state when there are no records to display.

Areas to inspect first:

internal/httpapi/help/static/
internal/httpapi/help/static/graphs/
internal/httpapi/help/static/graphs/context-graph/
internal/httpapi/help/static/graphs/authority-graph/
internal/httpapi/help/static/search/

The contributor should identify the relevant Explorer frontend files before making changes.

The improvement should distinguish between:

• loading state;
• no data available;
• no results for current search/filter;
• failed fetch or unavailable endpoint;
• empty graph because no relevant MIDAS resources exist yet.

Acceptance Criteria

• Explorer shows clear user-facing empty-state text in the relevant graph/catalogue views.
• Empty states explain what the user can do next where appropriate.
• Search/filter empty states are distinct from “no data exists” states.
• Error states are not presented as ordinary empty states.
• Existing graph rendering behaviour is not changed.
• Existing data loading behaviour is not changed.
• No backend API changes are made.
• No new dependencies are added.
• Existing frontend tests, if present, continue to pass.
• go test ./internal/httpapi/... or the relevant existing test package passes.
• git diff --check passes.

Suggested copy style

Use short, practical messages such as:

No decision surfaces found.
Create or apply a control-plane bundle to populate this view.

or:

No results match the current search.
Clear the search or adjust the filter to see more records.

Out of Scope

• Redesigning Explorer.
• Changing graph layout behaviour.
• Changing Cytoscape configuration.
• Adding new graph features.
• Changing backend APIs.
• Adding new data sources.
• Adding new dependencies.