fix(release): derive versionCode from build time, versionName from commit time

versionCode was `git rev-list --count HEAD`, and build.gradle.kts called it
"monotonic forever". It is not, and that claim was sitting directly above
the bug it denied.

A commit count runs ahead on `dev`. So a dev build carried a HIGHER code
than the `main` release meant to supersede it, and Android refuses that
install as a downgrade — a channel you can enter and cannot leave without
uninstalling and losing local data.

Two clocks now, and the split is deliberate even though it reads like an
inconsistency:

The NAME answers "is this the same code?", so it derives from COMMIT time
and reads identically on every lane building this source. A dev build and
a main build of one commit must report the same string. Build time cannot
do that — it prints two numbers for one thing.

The ORDERING KEY answers "may this be installed over that?", so it must be
monotonic BY CONSTRUCTION: minutes since 2020-01-01. Commit time fails
here for the mirror-image reason — rebuild an older commit and it goes
DOWN, which on a phone is a refused install rather than a confusing label.

The non-tag :latest path reconstructed the bundled APK's name with the old
formula, so it is moved to the same commit-timestamp derivation. That
duplication is temporary: once the tag becomes `v<version-name>` it
collapses to `${TAG#v}` with nothing left to keep in step.

Verified locally by running the derivations rather than reasoning about
them: HEAD yields 2026.09.09.1828; the key yields 3519456 against ~1895
from the old scheme, inside int32 with ~4000 years of headroom; a commit
at 00:42 UTC yields "0042", not "42". The workflow now asserts the emitted
shape too — a malformed name builds, signs and publishes happily and only
surfaces as an update nobody is offered, which nobody reports.

That local check is the only verification this commit gets. release.yml
triggers on main and tags only, so nothing on `dev` executes the new
derivation; CI here proves the Gradle file still parses and nothing else.

Also confirms the migration constraint recorded in milestone #390: this
commit would name a release 2026.09.09.1828, which is LOWER than the
installed 2026.09.09.1895 under name comparison. The first new-scheme
release must be cut on a later calendar day, or existing installs will
never be offered it.

Step 1 of 5 — Scribe task #3808, milestone #390.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SQ31KQpYbStyK5y58UmPLH

android/app/build.gradle.kts

@@ -21,13 +21,24 @@ android {
         applicationId = "com.fabledsword.minstrel"
         minSdk = 26
         targetSdk = 36
-        // versionName / versionCode are released-build values injected by
-        // CI from the git tag + commit count. Local / debug builds fall
-        // back to "dev" so the About card reads honestly. Releases ship
-        // versionName="YYYY.MM.DD.<commits>" (e.g. "2026.06.02.142") and
-        // versionCode=<commits>, which is monotonic forever and lets the
-        // shared isVersionNewer comparator distinguish two same-day
-        // re-cuts (the iteration suffix differs).
+        // versionName / versionCode are released-build values injected by CI.
+        // Local / debug builds fall back to "dev" so the About card reads
+        // honestly.
+        //
+        // versionName is "YYYY.MM.DD.HHMM" from the COMMIT's timestamp, so
+        // every lane building this source reports the same string and the
+        // channel is the only thing that differs between them.
+        //
+        // versionCode is minutes since 2020-01-01 at BUILD time. It is the
+        // value the platform decides installs by, so it must be monotonic by
+        // construction.
+        //
+        // This comment used to say versionCode was a commit count and that it
+        // was "monotonic forever". It was neither — a commit count runs ahead
+        // on `dev`, so a dev build outranked the `main` release meant to
+        // replace it and Android refused the install as a downgrade. Worth
+        // knowing the claim was here, stated as a reassurance, while the bug
+        // it denied was live.
         val versionNameOverride =
             (project.findProperty("MINSTREL_VERSION_NAME") as String?)?.takeIf { it.isNotBlank() }
         val versionCodeOverride =