Harden Multipath Stream Discovery

Why

Google Maps now has both a file/import path and an API-backed Data Portability path, and agent hosts still vary in how much MCP tool output they expose. The reference needs a durable rule for reusing stream definitions across acquisition paths without erasing source identity, and MCP search needs to put a usable fetch handle where clipped previews still show it.

What Changes

• Define the reference construction rule for multipath collection: stream definitions may be reused across connectors and acquisition paths, but records remain scoped by connection_id / connector_instance_id.
• Allow multiple acquisition paths to populate one logical connection only when an explicit source-identity rule proves they are the same owner source; otherwise they remain separate connections that may share stream definitions.
• Require acquisition-path provenance to stay visible in run/coverage/source metadata without replacing disclosure identity.
• Harden MCP search text by surfacing a parseable first fetch handle before verbose source metadata, while keeping structuredContent.results canonical.

Capabilities

New Capabilities

• None.

Modified Capabilities

• reference-connector-instances: codify reusable stream definitions across acquisition paths, plus the identity bar for coalescing paths under one connection.
• mcp-adapter: require model-visible search text to expose a first fetch handle before host-clipped metadata.

Impact

• Affected code: packages/mcp-server/src/tools.js.
• Affected tests: MCP self-contained result-id/search-fetch tests.
• No database migration, REST contract change, provider OAuth change, or connector runtime implementation is required in this tranche.