feat(protos): add Postgres + Supabase config messages (Phase 3c)

[ihistand]

Summary

Phase 3c of `adapter/postgres-first-class` per `docs/postgres_first_class_design.md` §3 + §8.2.

Adds the proto messages the Postgres-first-class adapter needs. Additive only — nothing references these yet. Wiring happens in subsequent phases.

Added messages

Action-level option blocks (peers of the existing inlined BigQuery fields)

Message	Purpose
`PostgresOptions`	`tablespace`, `fillfactor`, `unlogged`, native declarative partitioning (RANGE/LIST/HASH), btree/gin/gist/hash/brin indexes, materialized view refresh policy
`SupabaseOptions`	Realtime publication, RLS enable, owner role, pgvector convenience config; nests `PostgresOptions`

Top-level connection config (will live under `WorkflowSettings.warehouse` in Phase 4)

Message	Purpose
`BigQueryConnection`	`project`, `location`, `default_dataset`
`PostgresConnection`	libpq-style: `host`, `port`, `database`, `user`, `password`, `ssl_mode`, `default_schema`
`SupabaseConnection`	`project_ref`, `service_role_key`, `default_schema`, optional direct `connection_string` override
`WarehouseConfig`	Discriminated union over the three connection variants via `oneof connection`

Why additive only

Wiring `PostgresOptions` into `ActionConfig.TableConfig` etc. requires choosing field numbers across 4 messages (TableConfig, ViewConfig, IncrementalTableConfig, OperationConfig) and is a separate concern. Same for `WarehouseConfig` → `WorkflowSettings.warehouse`, which collides semantically with the legacy flat `default_project` / `default_dataset` / `default_location` fields and needs careful migration.

The messages exist; consumers come next.

Verification

```bash
./scripts/docker-bazel build //protos:ts # → success
./scripts/docker-bazel build //... # → success (139 targets)
```

Stack

Stacked on PR #5 (`adapter/postgres-relocate`). Merge order: #1 → #2 → #3 → #4 → #5 → this.

Next phases

• Phase 3a — `PostgresDbAdapter` against current `IDbAdapter` contract; consumes `PostgresConnection`
• Phase 4 — wire `WorkflowSettings.warehouse`; CLI dispatches on `warehouse.kind`
• Phase 5 — `SupabaseDbAdapter` + `rlsPolicy`/`realtimePublication`/`wrapper`/`vectorIndex` action types consume `SupabaseOptions`

Test plan

• `./scripts/docker-bazel build //protos:ts`
• `./scripts/docker-bazel build //...` (139 targets)
• Wiring into ActionConfig sub-messages (Phase 3a/4)

🤖 Generated with Claude Code

[ihistand]

Superseded: the Postgres reintegration + Dataform→SQLAnvil rename landed on main directly, and the docs moved to the SQLAnvil/docs repo. Closing as part of #12 (stale-branch prune). The one un-migrated draft, gcp_test_project_setup.md, was migrated to SQLAnvil/docs.