capsite/lib: MapStore and patterns work-alikes

Enough of @agoric/store's MapStore and @endo/patterns' M for the
credential-rotation design: makeMapStore(label, { keyShape, valueShape },
kv) keeps entries in a DO's sync KV under store:<label>:, and readOnly()
hands out the queries alone. Facets are workerd RpcTargets in place of
endo's Far.

Unlike endo, error messages never include keys or values: the values
here are credentials, and messages cross RPC into logs.

Generated-by: Claude Opus 5.5

lib/package.json

@@ -0,0 +1,16 @@
+{
+	"name": "capsite-lib",
+	"private": true,
+	"type": "module",
+	"scripts": {
+		"types": "wrangler types -c wrangler.tests.jsonc",
+		"lint": "wrangler types -c wrangler.tests.jsonc --check && tsc -p tsconfig.json && tsc -p tests/tsconfig.json",
+		"test": "vitest run"
+	},
+	"devDependencies": {
+		"@cloudflare/vitest-plugin": "1.3.6",
+		"typescript": "^5.9.0",
+		"vitest": "4.1.11",
+		"wrangler": "^4.148.0"
+	}
+}