fix(explore): state rootDir for the tool build, which tsc-alias requires

Restoring the paths map got tsc through, and the image build moved on to the
next command on the same line:

  > tsc -p ./tsconfig.json && tsc-alias -p ./tsconfig.json
  tsc-alias error: compilerOptions.rootDir is required with implicit baseUrl

tsc infers a rootDir from the inputs and is content; tsc-alias will not, and
without baseUrl there is nothing for it to fall back to. The inferred value was
already the repo root — the emit lands in build/configs, build/lib, build/ui —
so stating it changes no output. Verified by emitting either way: the JS tree is
identical, and only tsconfig.tsbuildinfo moves, since its path is computed
relative to rootDir.

deploy/tools/feature-reporter/tsconfig.json

@@ -6,6 +6,11 @@
     "module": "node16",
     "moduleResolution": "node16",
     "outDir": "./build",
+    // The repo root, which is where every input below already resolves to, so
+    // the emitted tree is unchanged. Stated because dropping baseUrl left it
+    // implicit, and tsc-alias — which runs straight after tsc — refuses that:
+    // "compilerOptions.rootDir is required with implicit baseUrl".
+    "rootDir": "../../..",
     // Every alias the include-set reaches must be listed here, because
     // TypeScript REPLACES the inherited paths map rather than merging it.
     // This was survivable while the root config set baseUrl: bare specifiers