build(js): upgrade TypeScript to 6.0 (both clients) (#346)

build(js): upgrade TypeScript to 6.0

Upgrade both JS clients to typescript@^6.0.3.

clients/js (modern, tsup):
- Add "rootDir": "./src" to tsconfig.declarations.json (TS6 requires an
  explicit rootDir for declaration emit; TS5011).

clients/js-legacy (tsc --build):
- tsconfig.base.json: add "ignoreDeprecations": "6.0" (node10/"Node"
  resolution is deprecated, TS5107), "lib": ["ES2020", "DOM"] (the cjs
  project targets ES2016 and the source uses BigInt, TS2583), and
  "types": ["node"] (so Buffer/http/https resolve, TS2591).
- tsconfig.cjs.json / tsconfig.esm.json: add "rootDir": "./src" (TS5011).
- tsconfig.json: "types": ["node", "mocha"] so the test build sees
  mocha's globals after the base "types" narrowing.

Each change corresponds to an actual TS6 compiler error observed when
building unmodified; no extra options were added.

Verified locally with typescript@6.0.3:
- clients/js: `pnpm build` + `pnpm lint` pass.
- clients/js-legacy: `pnpm build`, `pnpm lint`, and `pnpm test:exports`
  pass. The mocha integration tests (basic/longRecord) require a local
  validator and were not run here.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: clankmaxxing-clod

clients/js-legacy/package.json

@@ -57,7 +57,7 @@
         "mocha": "^11.7.6",
         "prettier": "^3.8.3",
         "shx": "^0.4.0",
-        "typescript": "^5.7.2",
+        "typescript": "^6.0.3",
         "start-server-and-test": "^3.0.5",
         "ts-node": "^10.9.2",
         "typescript-eslint": "^8.60.0"

clients/js-legacy/pnpm-lock.yaml

@@ -9,6 +9,9 @@
         "noEmitOnError": true,
         "resolveJsonModule": true,
         "strict": true,
-        "stripInternal": true
+        "stripInternal": true,
+        "ignoreDeprecations": "6.0",
+        "lib": ["ES2020", "DOM"],
+        "types": ["node"]
     }
 }

clients/js-legacy/tsconfig.base.json

@@ -7,6 +7,7 @@
         "outDir": "lib/cjs",
         "target": "ES2016",
         "module": "CommonJS",
-        "sourceMap": true
+        "sourceMap": true,
+        "rootDir": "./src"
     }
 }

clients/js-legacy/tsconfig.cjs.json

@@ -10,6 +10,7 @@
         "module": "ES2020",
         "sourceMap": true,
         "declaration": true,
-        "declarationMap": true
+        "declarationMap": true,
+        "rootDir": "./src"
     }
 }

clients/js-legacy/tsconfig.esm.json

@@ -6,6 +6,7 @@
     ],
     "compilerOptions": {
         "noEmit": true,
-        "skipLibCheck": true
+        "skipLibCheck": true,
+        "types": ["node", "mocha"]
     }
 }

clients/js-legacy/tsconfig.json

@@ -57,7 +57,7 @@
         "rimraf": "^6.1.3",
         "tsup": "^8.5.1",
         "typedoc": "^0.28.19",
-        "typescript": "^5.9.3",
+        "typescript": "^6.0.3",
         "vitest": "^4.0.15"
     },
     "peerDependencies": {