build(js-legacy): upgrade TypeScript to 6.0 (#104)

Bump typescript to ^6.0.3 in clients/js-legacy and adjust the tsc-based
build for TS6:

- tsconfig.base.json: add "ignoreDeprecations": "6.0" (the node10/"Node"
  module resolution is deprecated in TS6, TS5107) and "types": ["node"]
  so Buffer/http/https globals from @types/node resolve (TS2591 under the
  classic resolver).
- tsconfig.cjs.json / tsconfig.esm.json: add "rootDir": "./src" — TS6
  requires an explicit rootDir for these composite projects (TS5011).
- tsconfig.json: set "types": ["node", "mocha"] so the test build still
  sees mocha's globals after the base "types" narrowing.

Module resolution is left as-is and no lib override is added; only the
options TS6 actually requires were changed.

Verified locally with typescript@6.0.3: `pnpm build` (tsc --build),
`pnpm lint` (eslint), and `pnpm test` (mocha, 7 passing) all pass.

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

Author: clankmaxxing-clod

clients/js-legacy/package.json

@@ -72,7 +72,7 @@
         "ts-node": "^10.9.2",
         "tslib": "^2.8.1",
         "typedoc": "^0.28.19",
-        "typescript": "^5.7.2"
+        "typescript": "^6.0.3"
     },
     "prettier": "@solana/prettier-config-solana"
 }

clients/js-legacy/tsconfig.base.json

@@ -9,6 +9,8 @@
         "noEmitOnError": true,
         "resolveJsonModule": true,
         "strict": true,
-        "stripInternal": true
+        "stripInternal": true,
+        "ignoreDeprecations": "6.0",
+        "types": ["node"]
     }
 }

clients/js-legacy/tsconfig.cjs.json

@@ -5,6 +5,7 @@
         "outDir": "dist/cjs",
         "target": "ES2016",
         "module": "CommonJS",
-        "sourceMap": true
+        "sourceMap": true,
+        "rootDir": "./src"
     }
 }

clients/js-legacy/tsconfig.esm.json

@@ -8,6 +8,7 @@
         "module": "ES2020",
         "sourceMap": true,
         "declaration": true,
-        "declarationMap": true
+        "declarationMap": true,
+        "rootDir": "./src"
     }
 }

clients/js-legacy/tsconfig.json

@@ -3,6 +3,7 @@
     "include": ["src", "test"],
     "compilerOptions": {
         "noEmit": true,
-        "skipLibCheck": true
+        "skipLibCheck": true,
+        "types": ["node", "mocha"]
     }
 }