Port postgres to Go and install the extensions a consumer asks for

letta crash-loops on 'type "vector" does not exist': pgvector is not a
trusted extension, so only the provider's superuser can create it, and
the provisioner never did. A contribution may now name extensions; the
provider creates each (IF NOT EXISTS, available ones only) in the
consumer's database on every pass. Go per the standing rule for a
TypeScript module that changes. letta asks for vector.

modules/postgres/cmd/postgres-provider/tools.go

@@ -0,0 +1,98 @@
+package main
+
+// postgres's tools, and the mesh-store seat's verbs (novox/hq ADR 0159, 0160). The seat's verbs are
+// named `mesh-store.<verb>`, so the runtime serves them as the seat's wherever this module holds it
+// and never lists them as postgres's own; they are scoped to what the store enables — asking what it
+// holds and reading from it — so retiring a database is postgres's tool and not the store's.
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// Seat is the store seat this module claims.
+const Seat = "mesh-store"
+
+var queryInput = map[string]any{
+	"database": map[string]any{"type": "string", "description": "the database to query"},
+	"sql":      map[string]any{"type": "string", "description": "the SELECT (or other read-only) statement"},
+}
+
+func str(args map[string]any, key string) string {
+	if s, ok := args[key].(string); ok {
+		return s
+	}
+	return ""
+}
+
+func listTool(pg *Client, name, description string) stdio.Tool {
+	return stdio.Tool{Name: name, Description: description, Run: func(map[string]any) (any, error) {
+		ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+		defer cancel()
+		dbs, err := pg.ListDatabases(ctx)
+		if err != nil {
+			return nil, err
+		}
+		return map[string]any{"databases": dbs}, nil
+	}}
+}
+
+func queryTool(pg *Client, name, prefix, description string) stdio.Tool {
+	return stdio.Tool{Name: name, Description: description, Input: queryInput, Run: func(args map[string]any) (any, error) {
+		database, sql := str(args, "database"), str(args, "sql")
+		if database == "" {
+			return nil, fmt.Errorf("%s: database is required", prefix)
+		}
+		if sql == "" {
+			return nil, fmt.Errorf("%s: sql is required", prefix)
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
+		defer cancel()
+		r, err := pg.ReadOnlyQuery(ctx, database, sql)
+		if err != nil {
+			return nil, err
+		}
+		return map[string]any{"database": database, "command": r.Command, "rows": r.Maps()}, nil
+	}}
+}
+
+// Tools are postgres's own and the seat's verbs.
+func Tools(pg *Client) []stdio.Tool {
+	return []stdio.Tool{
+		listTool(pg, "postgres_list_databases", "List the databases on the postgres server, with their on-disk size."),
+		queryTool(pg, "postgres_query", "postgres_query",
+			"Run a read-only SQL query against a named database, as a login that can read every table and change nothing."),
+		{
+			Name: "postgres_retire_database",
+			Description: "Take one database out of service on purpose: rename it to <name>_deleted_<date> and lock its owner's login. " +
+				"Nothing is dropped — the data stays on the server under the new name until a person removes it by hand. " +
+				"Repeat the database's name in confirm.",
+			Input: map[string]any{
+				"database": map[string]any{"type": "string", "description": "the database to retire"},
+				"confirm":  map[string]any{"type": "string", "description": "the same name again, to say this is meant"},
+			},
+			Run: func(args map[string]any) (any, error) {
+				database := str(args, "database")
+				if database == "" {
+					return nil, errors.New("postgres_retire_database: database is required")
+				}
+				if str(args, "confirm") != database {
+					return nil, errors.New("postgres_retire_database: confirm must repeat the database's name")
+				}
+				ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+				defer cancel()
+				aside, err := pg.RetireDatabase(ctx, database, time.Now())
+				if err != nil {
+					return nil, err
+				}
+				return map[string]any{"database": database, "renamedTo": aside, "dropped": false}, nil
+			},
+		},
+		listTool(pg, Seat+".databases", "Every database the store holds, with its on-disk size."),
+		queryTool(pg, Seat+".query", "query", "One read-only statement against one database the store holds."),
+	}
+}