feat: bfb scroll sub-command

[tellet-q]

Scroll was only reachable as a --scroll flag as a part of a full benchmark run, so timing it meant re-uploading first. This makes it a subcommand that runs against a collection that already exists: bfb scroll --file examples/scroll-config.yaml -n 50k -p 8 --json scroll.json. Results land under results.scroll, same shape as results.search. The YAML describes the shape of scroll requests — the collection, and the payload filters to scroll by. One template is picked at random per request with fresh filter values, so a single run can compare filtered against unfiltered:

  collection:                                                                                                                                                                                                                                 
    name: benchmark

  mode: scroll|sequential|sample
                                                                                                                                                                                                                                              
  requests:                                                                                                                                                                                                                                   
    - filters: []          # unfiltered                                                                                                                                                                                                       
    - filters:                                                                                                                                                                                                                                
        - name: color                                                                                                                                                                                                                         
          type: keyword                                                                                                                                                                                                                       
          source: { type: random, cardinality: 100 }

Filter entries use the same payload type / source vocabulary as the upload and search configs, because it's now literally the same code, with no change in behavior.

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[Copilot]

Pull request overview

Adds a dedicated bfb scroll subcommand so scroll workloads can be executed and reported independently against an already-existing collection, using a YAML config to describe scroll request “shapes” (collection + payload filters). This complements the existing flag-driven --scroll path while aligning scroll’s filter generation with the YAML-config-driven search path.

Changes:

• Introduces bfb scroll --file … with a new YAML scroll config (src/config/scroll.rs) and CLI wiring (src/args/mod.rs, src/main.rs, src/query.rs).
• Refactors YAML filter generation into a reusable FilterGenerator shared by YAML search and YAML scroll (src/generators/queries.rs).
• Documents the new workflow and provides an example config (README.md, examples/scroll-config.yaml).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/scroll.rs	Adds config-driven filter selection for scroll requests (new Filters source abstraction).
src/query.rs	Exposes scroll_with_config entrypoint for YAML-config-driven scroll.
src/main.rs	Wires the new scroll subcommand into the main dispatch and results output.
src/generators/queries.rs	Extracts/centralizes YAML payload filter generation into FilterGenerator and reuses it for search.
src/config/scroll.rs	Adds YAML schema/types + loader/validation for scroll configs (with tests).
src/config/mod.rs	Exposes the new config::scroll module.
src/args/mod.rs	Adds Command::Scroll and ScrollArgs { --file } for clap parsing.
README.md	Documents bfb scroll usage and output location under results.scroll.
examples/scroll-config.yaml	Provides a concrete scroll config example for users.

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