ops: push legacy-import to codeforphilly-data and merge into main

[themightychris]

The JSON importer writes a snapshot commit on a local legacy-import
branch of the data repo but does not push or merge — those are deliberate
operator steps.

To integrate an importer run into runtime data:

1. After running the importer locally:

   ```bash
   cd /path/to/codeforphilly-data
   git push origin legacy-import
   ```

2. Open a PR on `CodeForPhilly/codeforphilly-data` from `legacy-import` to
   `main`. The PR diff will be massive on the first run (44k files) and
   small on subsequent runs (just the records that changed upstream).

3. Review the diff:

   • Path-shape conflicts: the importer writes `projects/.toml`
     while the runtime spec's gitsheets config uses `projects/.toml`
     path templates. Resolve by renaming files at merge time, or by
     accepting a one-time `.gitsheets/` config swap on the legacy-import
     branch before the first merge. Document the chosen approach here for
     the next time.
   • Records edited on `main` since the last merge will surface as merge
     conflicts (per the test in feat(importer): JSON-based laddr import producing legacy-import branch snapshots #57's plan). Resolve manually.

4. Merge.

This is intentionally manual because the merge is a runtime-data-affecting
step that warrants human review at cutover time.

Surfaced during the `laddr-import-via-json` plan (PR #57).