Check every JNI symbol, not just the first one

The android-check job failed on a tree that is perfectly correct:
android.rs exports three `Java_..._MainActivity_*` symbols, the check
compared all three against a single expected name and called it a
mismatch.

Two bugs, both from assuming one native:

- SYM collected every export while EXPECTED was built from one method, so
  the comparison was three lines against one.
- The Kotlin side matched `external fun name()` on empty parens, which
  quietly skipped nativeSetActivity and nativeBluetoothStateChanged —
  parameters do not appear in the symbol name, so stop at the paren.

Now both sides are collected into sets and diffed, so a native declared
in Kotlin with no Rust half fails as loudly as the reverse. Verified
against the real files: passes as-is, and fails with a readable diff for
a Kotlin-only native and for a renamed Rust export.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-and-test.yml

@@ -138,7 +138,7 @@ jobs:
 
       # Cheap invariants that a compiler cannot see. Both failures are silent:
       # the app builds, installs, launches, and then finds no trainer.
-      - name: Check the Android source layout and the JNI symbol
+      - name: Check the Android source layout and the JNI symbols
         run: |
           set -e
           # gen/ is generated and must stay untracked, or a `tauri android init`
@@ -152,20 +152,35 @@ jobs:
           KT=src-tauri/android/src/main/java/paris/tourolle/bikecontrol/MainActivity.kt
           [ -f "$KT" ] || { echo "❌ $KT is missing"; exit 1; }
 
-          # The JNI symbol in android.rs is matched by the *runtime*, by name.
-          # Rename the Kotlin package or the method and nothing fails to
-          # compile — btleplug simply never gets initialised.
-          SYM=$(sed -n 's/.*pub extern "system" fn \(Java_[A-Za-z0-9_]*\).*/\1/p' src-tauri/src/android.rs)
+          # JNI symbols are matched by the *runtime*, by name. Rename the
+          # Kotlin package, add a native without its Rust half, or drop a Rust
+          # export, and nothing fails to compile — the method simply is not
+          # there when Java calls it. So compare the two sets, both ways.
+          #
+          # Sets, not a single pair: there are three natives now, and matching
+          # `external fun name()` on empty parens missed the two that take
+          # arguments. Parameters do not appear in the symbol name, so stop at
+          # the opening paren.
+          TMP="${RUNNER_TEMP:-/tmp}"
           PKG=$(sed -n 's/^package \(.*\)$/\1/p' "$KT" | tr -d '\r')
-          METHOD=$(sed -n 's/.*external fun \([A-Za-z0-9_]*\)().*/\1/p' "$KT")
-          EXPECTED="Java_$(echo "$PKG" | tr '.' '_')_MainActivity_$METHOD"
-          if [ "$SYM" != "$EXPECTED" ]; then
-            echo "❌ JNI symbol mismatch:"
-            echo "     android.rs exports: $SYM"
-            echo "     MainActivity needs: $EXPECTED"
+          PREFIX="Java_$(echo "$PKG" | tr '.' '_')_MainActivity_"
+
+          sed -n 's/.*pub extern "system" fn \(Java_[A-Za-z0-9_]*\).*/\1/p' \
+            src-tauri/src/android.rs | sort -u > "$TMP/jni-rust"
+          sed -n "s/.*external fun \([A-Za-z0-9_]*\)(.*/$PREFIX\1/p" \
+            "$KT" | sort -u > "$TMP/jni-kotlin"
+
+          [ -s "$TMP/jni-rust" ] || { echo "❌ No JNI exports found in android.rs"; exit 1; }
+
+          if ! diff -u "$TMP/jni-kotlin" "$TMP/jni-rust" > "$TMP/jni-diff"; then
+            echo "❌ JNI symbols differ between MainActivity.kt and android.rs:"
+            echo "     -  declared in MainActivity.kt, not exported by android.rs"
+            echo "     +  exported by android.rs, not declared in MainActivity.kt"
+            tail -n +4 "$TMP/jni-diff"
             exit 1
           fi
-          echo "✅ JNI symbol $SYM matches $PKG.MainActivity.$METHOD"
+          echo "✅ $(wc -l < "$TMP/jni-rust") JNI symbols match $PKG.MainActivity:"
+          sed 's/^/     /' "$TMP/jni-rust"
 
       - name: Cargo check (aarch64-linux-android)
         run: |