Add Azure Synapse connector

[luca-martial]

Scope

Build packages/connector-synapse/ for introspecting Azure Synapse Analytics (dedicated SQL pool and serverless SQL pool).

Where to start

• Model on packages/connector-sqlserver/ — Synapse uses T-SQL and is closest to SQL Server
• Use the mssql npm package (Tedious driver) for the wire protocol
• Introspection via sys.tables, sys.columns, and sys.schemas
• Auth supports Azure AD service principal or SQL credentials
• Wire the new driver in packages/context/src/project/driver-schemas.ts
• Add docs in docs-site/content/docs/integrations/primary-sources.mdx

Acceptance criteria

• @kaelio/connector-synapse package builds, type-checks, and tests pass
• Supports both dedicated SQL pool and serverless SQL pool endpoints
• Authentication: Azure AD service principal at minimum (SQL auth as fallback)
• Read-only SQL execution
• Integration docs added with a connection-config example

Reward

Merging this PR earns the hoodie tier (tier-3). See CONTRIBUTING.md.

Comment on this issue to claim it before starting work.

[sailingsam]

@luca-martial I would like to work on this issue! By the time you can review PR-#344 I have raised for #166.