bundle/schema/jsonschema_for_docs.json was a checked-in generated artifact on
main, but nothing in the CLI reads it — the binary embeds jsonschema.json, and
bundle/docsgen regenerates from Go types. Its only consumer is downstream docs
tooling, which now reads the schema from the docgen branch.

- Delete bundle/schema/jsonschema_for_docs.json and remove generate-schema-docs
  from the `all`/`generate` aggregators and the Taskfile, so `task generate` no
  longer recreates it on main. (generate-check, the CI drift subset, already
  excluded it.)
- The update-schema-docs workflow now regenerates the schema straight into the
  docgen worktree and commits it there, instead of generating on main and
  copying. Drops the now-unneeded "assert only the docs schema changed on main"
  and capture steps.
- Drop the file from .wsignore, .gitattributes, and the auto-generated-files
  rule.

Co-authored-by: Isaac