Kheiss/fix build

[kheiss-uwzoo]

Fix documentation build warnings and broken references

Summary

Resolves MkDocs build warnings and broken links reported during mkdocs build, so the docs build completes cleanly without nav/link errors.

Changes

Navigation (docs/mkdocs.yml)

• Removed invalid nav entry: API Reference: extraction/api-docs
  The path extraction/api-docs does not exist. The existing “Use the API” item already points to extraction/python-api-reference.md.

Links and anchors

• docs/docs/extraction/user-defined-functions.md

  • Replaced the relative link to ../../../config/default_pipeline.yaml (outside the docs tree, so MkDocs reported “target not found”) with a stable GitHub URL:
    https://github.com/NVIDIA/nv-ingest/blob/main/config/default_pipeline.yaml

• docs/docs/extraction/content-metadata.md

  • Added explicit fragment IDs so in-page links resolve correctly:
    • #nearbyobjectsschema → ### \NearbyObjectsSchema` (Currently Unused)`
    • #errormetadataschema → ### \ErrorMetadataSchema` (Currently Unused)`
    • #infomessagemetadataschema → ### \InfoMessageMetadataSchema` (Currently Unused)`

Build impact

After these changes, the following are addressed:

• A reference to 'extraction/api-docs' is included in the 'nav' configuration, which is not found
• Doc file 'extraction/user-defined-functions.md' contains a link ... but the target ... is not found among documentation files
• Doc file 'extraction/content-metadata.md' contains a link '#errormetadataschema' (#infomessagemetadataschema, #nearbyobjectsschema), but there is no such anchor on this page

Testing

• Run from repo root: mkdocs build -f docs/mkdocs.yml (or from docs/: mkdocs build) and confirm no nav/link warnings for the above items.

Notes

• client/uv.lock and any other non-docs changes on the branch are unrelated to this fix.
• If you reintroduce an “API Reference” nav item later (e.g. for generated API docs), add it once that page or directory exists under the docs tree.