Drop merged GraphQL schema for split files

Relay no longer needs a single merged schema.graphql: each project in
relay.config.json now reads the split graphql/*.graphql files directly
via `schema` (base.graphql) plus `schemaExtensions`. gqlgen already
consumed the split files, so the merge step only fed Relay and the
optional IDE GraphQL extension.

Remove the merge machinery (contrib/merge-graphql-schema.sh, the
RELAY_SCHEMAS make rules, and the gitignore entry) and drop the
graphql-config files (apps/trust/graphql.config.yml and the root
package.json graphql field); the Relay extension provides schema-aware
language features from relay.config.json on its own.

relay-compiler keeps generated artifacts in sync (stale ones are
removed automatically), so the relay npm script just runs the local
relay-compiler and the make target delegates to it.

Signed-off-by: Émile Ré <emile@probo.com>

contrib/claude/make.md

@@ -41,7 +41,7 @@ Individual codegen is driven by `go generate`:
 - `go generate ./pkg/server/api/mcp/v1` — MCP (mcpgen)
 - `go generate ./pkg/llm` — LLM model registry from OpenRouter (`make genmodels`)
 
-`make relay` merges split `.graphql` schema files and runs `relay-compiler`.
+`make relay` runs `relay-compiler`, which reads the split `.graphql` schema files directly (via each project's `schema` + `schemaExtensions` in `relay.config.json`) and keeps generated artifacts in sync (stale ones are removed automatically).
 
 ## Coverage