Initial commit: capability prober + design docs

Monorepo root for Echolot. Contains the no-root capability prober
(Kotlin/Compose, app.echo_lot.prober) and the four design docs that act
as the contract for the production app and the Go server.

LICENSE is deliberately absent — still undecided, see docs/build-status.md.

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

echolot-prober/app/src/main/res/values/strings.xml

@@ -0,0 +1,3 @@
+<resources>
+    <string name="app_name">Echolot Prober</string>
+</resources>

echolot-prober/app/src/main/res/values/themes.xml

@@ -0,0 +1,3 @@
+<resources>
+    <style name="Theme.EcholotProber" parent="android:Theme.Material.Light.NoActionBar" />
+</resources>

echolot-prober/app/src/main/res/xml/file_paths.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<paths>
+    <cache-path name="reports" path="reports/" />
+</paths>