fix(android): raise the versionCode floor so 0.5.x can install over v0.5.2

v0.5.2 shipped Android versionCode 5002, from an earlier `minor*1000` scheme.
The `minor*100` formula that replaced it yields only 1502 for that same version,
and 1503 for 0.5.3 — lower than what is already installed, so Android refuses
the update as a downgrade. Every 0.5.x release built from this script was
un-installable for anyone already on v0.5.2.

This is the exact failure the block was written to prevent; its floor simply
went stale. The floor tracked "codes below 1000 are already in the field", which
was true when written, but a 5002 build has shipped since — and the highest code
this formula has *produced* is not the same as the highest code in the field.

Widen the multipliers and raise the floor past 5002:

    code = 10000 + major*1000000 + minor*1000 + patch

    0.0.14 -> 10014    0.5.2 -> 15002    0.6.0 -> 16000
    0.1.0  -> 11000    0.5.3 -> 15003    1.0.0 -> 1010000

Still strictly monotonic across the upgrade sequence. The guard test gains a
case pinning 0.5.3 above the 5002 in the field, so the floor is expressed as
"clears what shipped" rather than a literal that can silently go stale again.

scripts/set-version.test.ts

@@ -106,21 +106,33 @@ describe("set-version.sh", () => {
   });
 
   describe("Android versionCode", () => {
-    // Codes below 1000 are already in the field; a newer release must never
-    // produce a smaller number than an older one.
-    it("clears the 1000 floor shipped by earlier builds", () => {
+    // A newer release must never produce a smaller number than an older one, or
+    // Android refuses the update. The floor tracks the highest code actually in
+    // the field, which is NOT the same as the highest this formula has produced:
+    // v0.5.2 shipped versionCode 5002 from an earlier `minor*1000` scheme, while
+    // the `minor*100` formula that replaced it yields only 1502 for that same
+    // version — so every 0.5.x release built from it was an un-installable
+    // downgrade for anyone already on v0.5.2. The floor is raised to clear it.
+    it("clears the highest code shipped by earlier builds", () => {
       run("0.0.1");
-      expect(versionCode()).toBeGreaterThan(1000);
+      // v0.5.2 shipped 5002; anything at or below that cannot install over it.
+      expect(versionCode()).toBeGreaterThan(5002);
     });
 
-    it("uses 1000 + major*10000 + minor*100 + patch", () => {
+    it("keeps 0.5.3 installable over the 5002 that shipped as v0.5.2", () => {
+      run("0.5.3");
+      expect(versionCode()).toBeGreaterThan(5002);
+    });
+
+    it("uses 10000 + major*1000000 + minor*1000 + patch", () => {
       const cases: Array<[string, number]> = [
-        ["0.0.14", 1014],
-        ["0.0.15", 1015],
-        ["0.1.0", 1100],
-        ["0.4.8", 1408],
-        ["0.5.0", 1500],
-        ["1.0.0", 11000],
+        ["0.0.14", 10014],
+        ["0.0.15", 10015],
+        ["0.1.0", 11000],
+        ["0.4.8", 14008],
+        ["0.5.0", 15000],
+        ["0.5.3", 15003],
+        ["1.0.0", 1010000],
       ];
       for (const [version, code] of cases) {
         seed(tmp);
@@ -145,7 +157,7 @@ describe("set-version.sh", () => {
     // stripped before the arithmetic.
     it("derives the code from the numeric core of a prerelease", () => {
       run("0.6.0-rc1");
-      expect(versionCode()).toBe(1600);
+      expect(versionCode()).toBe(16000);
       expect(JSON.parse(read("package.json")).version).toBe("0.6.0-rc1");
     });
   });