Pin open-data's shared dependency off main #2473

Blocker for the schema change. Small, but must land first.

The hazard

open-data validates every person record against our Official model, and it pins us to main:

# open-data/pyproject.toml:26-27
shared = {git = "…civicpatch-tools.git", subdirectory = "shared", branch = "main"}

# open-data/scripts/github_actions/validate_jurisdiction.py:33
Official(**person_data)

So the moment the new Official (with roles[], without office) merges to this repo's main, open-data CI starts rejecting all 3,430 un-backfilled person files — with no coordinated release and no way to stage the change.

This makes the office → roles[] migration effectively impossible to do safely today.

What to do

• Change the pin in open-data/pyproject.toml from branch = "main" to a tag or rev.
• Add a release/tag step to this repo so shared has versioned cut points.
• Document the bump procedure (open-data already has a mise task add-shared, see open-data/mise.toml:69-72).

Also fix while here

open-data/README.md:38 and open-data/CLAUDE.md:47 both claim open-data/schemas.py holds Jurisdiction, Office, Official. It holds only Jurisdiction — Office/Official live in shared/src/shared/schemas.py in this repo. The stale docs are exactly what makes this coupling easy to miss.

Verification

open-data CI green against a pinned shared while this repo's main moves ahead with an incompatible Official.

Part of the temporal-roles work — see the tracking issue for ordering.