chore(release): bump version to 2.1.6 (build 131)

Version: CURRENT_PROJECT_VERSION 130 -> 131 (project.yml, AGENTS.md, READMEs,
docs/llms.txt).

fix(flow): host-app identification now compiles in every build configuration
(Debug, TestFlight, Release). The arbiter probe and HostAppIdentity were
DEBUG-only, so TestFlight/App Store builds never knew the host bundle id and
could not auto-return after a startflow handoff. Debug-only logging and the
Home test card are unchanged.

Also includes the pending work in the tree:
- Home: single account/setup card surface (HomeAccountSurfacePolicy/Views)
- Wide screens: voice key row and centred mic placement, iPhone Duo layout
- Keyboard: clipboard skill ranking and AI skill layout updates
- Debug: account session handoff to the Simulator (+ import script)
- Docs: portfolio assets, privacy policy URL, site/README refresh

OSGKeyboardShared/Typing/VoiceMicPlacement.swift

@@ -0,0 +1,29 @@
+// VoiceMicPlacement.swift
+// OSGKeyboard · Shared
+//
+// Vertical placement of the voice surface's mic row. Every shell height
+// (phone, unfolded Duo, landscape, iPad narrow / wide) leaves a different
+// amount of free height between the top bar and the bottom row; this splits it
+// into the context slot above the mic and the gap below it with one rule, so
+// the mic sits centred in the area below the top bar on every device.
+
+import CoreGraphics
+
+public enum VoiceMicPlacement {
+    /// Never let the mic touch the bottom row.
+    public static let minimumGap: CGFloat = 10
+
+    /// Context slot height for a free height (`contextAndGap` = slot + gap).
+    /// Centred means the slot above the mic equals the gap plus the bottom row
+    /// below it, but the slot never drops under `minimumContextHeight` (the
+    /// live transcript) and the gap never under `minimumGap`.
+    public static func contextHeight(
+        contextAndGap: CGFloat,
+        bottomRowHeight: CGFloat,
+        minimumContextHeight: CGFloat
+    ) -> CGFloat {
+        let centred = (contextAndGap + bottomRowHeight) / 2
+        let ceiling = max(0, contextAndGap - minimumGap)
+        return min(ceiling, max(minimumContextHeight, centred))
+    }
+}