Add GET /queries stored-query catalog endpoint

List a graph's mcp.expose stored queries as a typed tool catalog so a client
(the MCP server) can register them as tools without fetching .gq source.
Each entry carries name, MCP tool_name, description/instruction, a
read/mutate flag, and decomposed typed params (kind enum: string|bool|int|
bigint|float|date|datetime|blob|vector|list, plus item_kind for lists and
vector_dim) — so the consumer builds an input schema with a closed match and
never re-parses omnigraph type spelling. I64/U64 are bigint (string on the
wire): a JSON number loses precision past 2^53 and the engine already accepts
decimal strings.

Read-gated (works in default-deny; the catalog is graph-wide, authorized
against main). NOT Cedar-filtered per query yet — a reader can list a query
whose invoke_query they lack (documented gap until per-query authz lands);
invocation stays invoke_query-gated + deny==404.

- api: QueriesCatalogOutput / QueryCatalogEntry / ParamDescriptor / ParamKind
  + query_catalog_entry (reuses PropType::from_param_type_name; scalar_kind is
  exhaustive, so a new ScalarType is a compile error here until catalogued).
- GET /queries route in per_graph_protected (→ /graphs/{id}/queries in multi
  mode); OpenAPI regenerated; path allowlists updated.
- Tests: projection unit (every kind, list, vector, nullable, mutation,
  empty) + handler (exposed-only filter, read-gate probe-oracle, empty
  registry).

openapi.json

@@ -829,6 +829,53 @@
         ]
       }
     },
+    "/queries": {
+      "get": {
+        "tags": [
+          "queries"
+        ],
+        "summary": "List the graph's exposed stored queries as a typed tool catalog.",
+        "description": "Returns the `mcp.expose == true` subset of the `queries:` registry, each\nwith its MCP tool name, read/mutate flag, description/instruction, and\ntyped parameters — enough for a client to register them as tools without\nfetching `.gq` source. Read-gated; the catalog is graph-wide (branch\nindependent — `read` is authorized against `main`). **Not** Cedar-filtered\nper query yet, so it can list a query whose `invoke_query` the caller\nlacks (a known gap until per-query authorization lands).",
+        "operationId": "list_queries",
+        "responses": {
+          "200": {
+            "description": "Stored-query catalog (the mcp.expose subset, with typed params)",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/QueriesCatalogOutput"
+                }
+              }
+            }
+          },
+          "401": {
+            "description": "Unauthorized",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorOutput"
+                }
+              }
+            }
+          },
+          "403": {
+            "description": "Forbidden",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorOutput"
+                }
+              }
+            }
+          }
+        },
+        "security": [
+          {
+            "bearer_token": []
+          }
+        ]
+      }
+    },
     "/queries/{name}": {
       "post": {
         "tags": [
@@ -1840,6 +1887,120 @@
           }
         }
       },
+      "ParamDescriptor": {
+        "type": "object",
+        "description": "One declared parameter of a stored query, projected for the catalog.",
+        "required": [
+          "name",
+          "kind",
+          "nullable"
+        ],
+        "properties": {
+          "item_kind": {
+            "oneOf": [
+              {
+                "type": "null"
+              },
+              {
+                "$ref": "#/components/schemas/ParamKind",
+                "description": "Element kind when `kind == list` (always a scalar — the grammar\nforbids lists of vectors or nested lists)."
+              }
+            ]
+          },
+          "kind": {
+            "$ref": "#/components/schemas/ParamKind"
+          },
+          "name": {
+            "type": "string"
+          },
+          "nullable": {
+            "type": "boolean",
+            "description": "`false` → the caller must supply it; `true` → optional."
+          },
+          "vector_dim": {
+            "type": [
+              "integer",
+              "null"
+            ],
+            "format": "int32",
+            "description": "Dimension when `kind == vector`.",
+            "minimum": 0
+          }
+        }
+      },
+      "ParamKind": {
+        "type": "string",
+        "description": "The kind of a stored-query parameter, decomposed so a client (e.g. an\nMCP server) can build a typed input schema with a closed `match` and\nnever re-parse omnigraph's type spelling. `bigint`/`date`/`datetime`/\n`blob` are carried as JSON strings on the wire: a 64-bit integer past\n2^53 loses precision as a JSON number, and Date/DateTime are ISO\nstrings, Blob a blob-URI string.",
+        "enum": [
+          "string",
+          "bool",
+          "int",
+          "bigint",
+          "float",
+          "date",
+          "datetime",
+          "blob",
+          "vector",
+          "list"
+        ]
+      },
+      "QueriesCatalogOutput": {
+        "type": "object",
+        "description": "Response for `GET /queries`: the `mcp.expose` subset of a graph's\nstored-query registry, each with typed parameters.",
+        "required": [
+          "queries"
+        ],
+        "properties": {
+          "queries": {
+            "type": "array",
+            "items": {
+              "$ref": "#/components/schemas/QueryCatalogEntry"
+            }
+          }
+        }
+      },
+      "QueryCatalogEntry": {
+        "type": "object",
+        "description": "One entry in the stored-query catalog (`GET /queries`).",
+        "required": [
+          "name",
+          "tool_name",
+          "mutation",
+          "params"
+        ],
+        "properties": {
+          "description": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "instruction": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "mutation": {
+            "type": "boolean",
+            "description": "`true` for a stored mutation → an MCP read-only hint of `false`."
+          },
+          "name": {
+            "type": "string",
+            "description": "Registry key / invoke path segment (`POST /queries/{name}`)."
+          },
+          "params": {
+            "type": "array",
+            "items": {
+              "$ref": "#/components/schemas/ParamDescriptor"
+            }
+          },
+          "tool_name": {
+            "type": "string",
+            "description": "MCP tool id (the `tool_name` override, else `name`)."
+          }
+        }
+      },
       "QueryRequest": {
         "type": "object",
         "description": "Inline read-query request for `POST /query`.\n\nFriendlier-named alternative to [`ReadRequest`] for ad-hoc reads and\nAI-agent integration. Mutations are rejected with 400 — use `POST\n/mutate` (or its deprecated alias `POST /change`) for write queries.\nField names are deliberately short (`query`, `name`) to match the GQ\nkeyword and the CLI `-e` flag.",