docs(extraction): add Customize & extend hub page

[kheiss-uwzoo]

Summary

• Add published Customize & extend page that surfaces UDF, custom graph pipeline, custom VDB, and coming-soon custom embedding paths with xrefs to repository guides.
• Replace section 8 nav link (previously graph README only) with the new page; redirect legacy \user-defined-functions\ and \user-defined-stages\ slugs.
• Cross-link from \concepts.md,
  eleasenotes.md, and \�dbs.md.

Follow-up to Randy's doc IA feedback (separate from #2276 starter-kits work).

Test plan

• \mkdocs build -f docs/mkdocs.yml --strict\
• \check-nrl-doc-leakage.ps1\
• Sidebar section 8 opens \customize-extend.md\
• Legacy /extraction/user-defined-functions/\ redirects after republish

Related

• docs(extraction): move Starter kits to examples/README.md (#2266 follow-up) #2276 — starter kits → \examples/README.md\ (separate PR)

[greptile-apps]

Greptile Summary

This PR adds a new Customize & extend hub page (extraction/customize-extend.md) that consolidates four extension paths—task configuration, UDFs, custom graph pipelines, and custom vector databases—with a decision table and links to in-repo guides. It replaces the raw GitHub README link in nav section 8, adds redirects for four legacy URLs, and cross-links from concepts.md and vdbs.md.

• customize-extend.md: New 66-line hub page with a decision table, per-section descriptions, and external GitHub guide links; includes a manual "On this page" TOC heading that may appear redundantly in the Material sidebar.
• mkdocs.yml: Nav section 8 points to the new local page; four redirect entries added, two with #fragment anchors (consistent with existing redirect patterns in the file).
• concepts.md / vdbs.md: Cross-links updated to point to the hub page instead of bare GitHub README URLs.

Confidence Score: 5/5

Documentation-only change; no code paths affected, strict MkDocs build verified, and all internal links resolve correctly.

All four changed files are Markdown or YAML nav configuration. The new hub page follows existing patterns for link targets and anchors, the redirect entries use #fragment syntax already established elsewhere in the redirects block, and the cross-links in concepts.md and vdbs.md replace external GitHub URLs with local relative paths that resolve under strict mode.

No files require special attention; the one style note on the manual TOC heading in customize-extend.md is cosmetic.

Important Files Changed

Filename	Overview
docs/docs/extraction/customize-extend.md	New hub page introducing four extension paths (task config, UDFs, custom graph, custom VDB) with a decision table and cross-links to repository guides; contains a manual "On this page" TOC heading that will also appear in the Material sidebar auto-TOC.
docs/mkdocs.yml	Nav section 8 updated from a bare GitHub link to the new local page; four legacy URL redirects added (two with #fragment anchors, consistent with existing project redirect patterns).
docs/docs/extraction/concepts.md	Two cross-links updated to reference the new customize-extend.md hub instead of the bare GitHub graph README URL.
docs/docs/extraction/vdbs.md	Two cross-references to customize-extend.md added: one inline in the custom operator paragraph, one in the Related Topics list.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    NAV["Nav: §8 Customize & extend"]
    CE["extraction/customize-extend.md"]
    CONCEPTS["concepts.md"]
    VDBS["vdbs.md"]

    NAV --> CE

    CONCEPTS -->|"#job cross-link"| CE
    CONCEPTS -->|"#pipeline-and-tasks cross-link"| CE
    VDBS -->|"inline + Related Topics"| CE

    subgraph Redirects
        R1["extraction/user-defined-stages.md"]
        R2["extraction/user-defined-functions/index.md"]
        R3["extraction/user-defined-functions.md"]
        R4["extraction/customize-and-extend.md"]
    end

    R1 -->|redirect| CE
    R2 -->|"redirect → #user-defined-functions-udfs"| CE
    R3 -->|"redirect → #user-defined-functions-udfs"| CE
    R4 -->|redirect| CE

    CE --> TC["#start-with-task-configuration"]
    CE --> UDF["#user-defined-functions-udfs"]
    CE --> GP["#custom-graph-pipelines"]
    CE --> VDB["#custom-vector-databases"]

Loading

%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
flowchart TD
    NAV["Nav: §8 Customize & extend"]
    CE["extraction/customize-extend.md"]
    CONCEPTS["concepts.md"]
    VDBS["vdbs.md"]

    NAV --> CE

    CONCEPTS -->|"#job cross-link"| CE
    CONCEPTS -->|"#pipeline-and-tasks cross-link"| CE
    VDBS -->|"inline + Related Topics"| CE

    subgraph Redirects
        R1["extraction/user-defined-stages.md"]
        R2["extraction/user-defined-functions/index.md"]
        R3["extraction/user-defined-functions.md"]
        R4["extraction/customize-and-extend.md"]
    end

    R1 -->|redirect| CE
    R2 -->|"redirect → #user-defined-functions-udfs"| CE
    R3 -->|"redirect → #user-defined-functions-udfs"| CE
    R4 -->|redirect| CE

    CE --> TC["#start-with-task-configuration"]
    CE --> UDF["#user-defined-functions-udfs"]
    CE --> GP["#custom-graph-pipelines"]
    CE --> VDB["#custom-vector-databases"]

Loading

_{Reviews (5): Last reviewed commit: "Merge branch 'main' into docs/customize-..." | Re-trigger Greptile}