Implement a new API to get schema dependents

[jviotti]

Signed-off-by: Juan Cruz Viotti jv@jviotti.com

[augmentcode]

🤖 Augment PR Summary

Summary: Adds a new API endpoint to expose “schema dependents” (reverse dependencies) for any indexed JSON Schema.

Changes:

• Introduces a new response schema for the dependents endpoint under the self/v1 collection.
• Documents GET /self/v1/api/schemas/dependents/{path} in the API docs.
• Extends the indexer to build a global dependency tree (dependency-tree.metapack) from per-schema dependency traces.
• Generates per-schema dependents.metapack artifacts by querying that dependency tree.
• Registers the new route in the precomputed router and wires a new server handler to serve dependents.metapack.
• Updates CLI output expectations/manifests and adds E2E hurl tests for the new endpoint.

Technical Notes: Dependents are computed as direct+transitive incoming edges; results are served as compressed JSON via the metapack pipeline.

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[augmentcode]

Review completed. 2 suggestions posted.

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