connector create: support snowflake + databricks dialects #1

Context

ana connector create today enumerates exactly one dialect:

// internal/connector/create.go:12
// v1 only supports the `postgres` dialect; other values are a usage error.
// ...
fs.Var(cli.EnumFlag(&typ, []string{"postgres"}), "type", "connector type (postgres — required)")

Anything else → usage error. Scripted provisioning of Snowflake / Databricks connectors therefore requires hitting the private RPC directly or using the UI.

Why it hurts

Came up mid-flow on a mock-data-forge demo: loaded a cross-source dataset (Snowflake + Databricks), needed two new connectors pointed at the freshly-loaded schemas, hit the CLI wall, had to context-switch to UI to finish the load step. Fine for one demo — painful for the recurring pattern this tool is meant to accelerate.

Other scripted flows likely blocked today:

• CI/CD provisioning of demo / test instances
• Bulk tenant onboarding
• Automated connector rotation (create new → flip references → delete old)
• Any runbook that wants to stand up a TextQL instance end-to-end from a repo

Proposed scope

Add --type snowflake and --type databricks with the dialect-specific flags each type needs. Rough sketch:

Snowflake

ana connector create --type snowflake --name <n> \
  --locator <acct-locator> --user <u> --database <db> --schema <s> \
  --warehouse <w> --role <r> \
  (--password-stdin | --private-key-file <path>)

Databricks

ana connector create --type databricks --name <n> \
  --host <host> --http-path <path> --catalog <cat> --schema <s> \
  (--pat-stdin | --oauth-m2m-client-id <id> --oauth-m2m-secret-stdin)

Server-side oneof spec blobs (snowflakeMetadata, databricksMetadata) already exist — this is a CLI plumbing issue, not a new backend capability.

Scope notes

• Secret handling: mirror the existing --password-stdin pattern. No plaintext secrets on argv.
• Auth variants: Snowflake keypair + Databricks OAuth M2M are the common "service account" forms — worth covering in v2, not v1-of-v2.
• Validation: ana connector test <id> already exists; creation can pipe into it for a dry-run.
• Update parity: ana connector update presumably has the same gap — worth pairing.