Add control board status scanner and MVP plan (#1503)

Step 1 of the control board MVP (decision MOSAIC-STACK-D-001): a plan page,
Gitea #1503, and packages/control-board, which reads each agent's newest pi
session log plus tmux liveness and writes one status file per agent under
<dataRoot>/board/. 23/23 tests; independent review approved after three
fixes (length stopReason as error, unknown liveness state, secrets-boundary
test). CURRENT.md now points at step 2, the page.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

packages/control-board/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "@mosaic/control-board",
+  "version": "0.1.0",
+  "private": true,
+  "description": "Control board MVP step 1: scan running agent sessions and write one status file per agent.",
+  "license": "UNLICENSED",
+  "type": "module",
+  "engines": { "node": ">=24" },
+  "bin": { "mosaic-board": "src/cli.mjs" },
+  "exports": {
+    ".": "./src/scan.mjs"
+  },
+  "scripts": {
+    "test": "node --test tests/"
+  }
+}