Port phase 1 to TypeScript

Move the standalone GameSense scale lighting to TypeScript ahead of the
Max for Live work, so step 3 gets type declarations at the seam.

Build emits CommonJS at ES2020 into dist/, because Node for Max loads CJS
on a Node version we do not control. bin/apex7-scale.js becomes a plain-JS
launcher so `node bin/apex7-scale.js` keeps working; the CLI itself moves
to src/cli.ts.

Two modules make previously implicit structure explicit:

  - src/protocol.ts, the GameSense wire types, so the transport and the
    payload construction agree on shapes neither of them owns
  - src/errors.ts, since `catch (err)` binds `unknown` under strict

Typing surfaced a few real fixes:

  - ScaleLighting.started was a public field the CLI set by hand to make
    --off work without start(); that is now release(), with started
    private behind isStarted
  - readAddress() trusted JSON.parse output; the address is now checked
    for being a non-empty string
  - res.statusCode is number|undefined, so the old `>= 200` comparison
    coerced silently; a missing status now rejects
  - parseIntervals claimed to dedupe and sort, and never did (comment
    corrected; pitchClassesFor is what dedupes)

Behavior is otherwise unchanged: all 18 tests pass and --once, --off,
--demo, --key-test, the resident stdin loop and the error paths were
verified against tools/fake-gamesense.ts.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tsconfig.json

@@ -0,0 +1,30 @@
+{
+  "compilerOptions": {
+    /* Node for Max (build step 3) loads CommonJS from a Node we do not
+       control, so emit plain CJS at a conservative language level. */
+    "target": "ES2020",
+    "lib": ["ES2020"],
+    "types": ["node"],
+    /* package.json has no "type", so node16 emits CommonJS. */
+    "module": "node16",
+    "moduleResolution": "node16",
+
+    "rootDir": ".",
+    "outDir": "dist",
+    "declaration": true,
+    "declarationMap": true,
+    "sourceMap": true,
+
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "noImplicitOverride": true,
+    "forceConsistentCasingInFileNames": true,
+
+    "esModuleInterop": true,
+    "skipLibCheck": true
+  },
+  "include": ["src/**/*.ts", "test/**/*.ts", "tools/**/*.ts"]
+}