Remove the REST Orbit graph_status endpoint

What does this MR do and why?

This MR removes the hidden REST route GET /api/v4/orbit/graph_status. The Orbit dashboard, the Duo readiness row, and the Orbit CLI read the same data from GraphQL.

Removed	Replacement
GET /api/v4/orbit/graph_status	Group.orbit and Project.orbit: indexing { state lastCompletedAt areas projects } and itemCounts

Changes

• ee/lib/api/orbit/data.rb: remove the route. Remove the orbit_status_route setting and the license branch that read it. No route sets it now.
• GrpcClient#get_graph_status and its map methods go.
• The orbit_graph_status rate limit goes.
• Regenerate the route list and the fine-grained token docs. OpenAPI and doc/api/orbit.md did not list the hidden route.

Parity on a local stack

We sent the REST route and the GraphQL fields for one group and one project, before the removal.

Target	Projects (indexed, known, gaps)	Item types	Item count sum	Count mismatches
Group gitlab-org	4, 4, 0 in both	31 in both	767,093 in both	0
Project gitlab-org/gitlab-test	1, 1, 0 in both	31 in both	99 in both	0

lastCompletedAt was the same in both. REST state indexed is GraphQL state READY.

GraphQL has no field for these REST values:

• The state of each item type.
• last_started_at, last_duration_ms, and last_error, for all indexing and for each area.
• The llm text format.

ai_workflows tokens can read indexing and itemCounts. The namespace request spec covers this.

References

• Stacked on !265633 (merged), which is merged.
• Removal plan: gitlab-org/orbit/knowledge-graph#263
• Orbit API docs: !265619 (merged) adds a "Rate limits" section to doc/api/orbit.md with an orbit_graph_status row. If that MR merges first, this MR deletes the row when it rebases. If this MR merges first, the docs MR deletes the row.
• The Orbit CLI uses GraphQL first and REST as a fallback: gitlab-org/orbit/knowledge-graph!3085 (merged) and gitlab-org/orbit/knowledge-graph!3144 (merged)

Screenshots or screen recordings

None. This MR has no UI change.

How to set up and validate locally

1. Send GET /api/v4/orbit/graph_status?full_path=<group>. The response is 404 Not Found.

MR acceptance checklist

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