## Why
Plugin and skill catalog reads currently wait for the Apps server's initial `tools/list` to finish, even after its MCP transport is initialized.
## What changed
Add the disabled-by-default `features.apps_early_resource_discovery` flag. When enabled, host-owned Apps requests for `mcp/plugin` and `mcp/skill` resources can use the initialized transport while the initial tool inventory is pending. Server readiness still waits for the inventory to complete, and retries use normal readiness.
Bound early client acquisition by the configured startup timeout, propagate startup failures and cancellation, and reject pages if the connection, authentication scope, or resource cache generation changes during discovery.
## Testing
Add coverage for gated discovery, concurrent plugin and skill reads, startup timeouts and failures, cancellation, cache invalidation, and account switches. Verify that early discovery reuses a single handshake and tool inventory, including with the newer MCP protocol and connection sharing enabled.
GitOrigin-RevId: 955b1f6d43b733bdf9763c1caf2ce6913c686c81
bkotsopoulos
9630b2e019