[borisr-code-ibm]

What I have done and why

Fixes #62

Problem

When Gemini calls an AppFunction tool, its JSON arguments are parsed by JsonElement.toPrimitive():
JSON numbers become Long/Double, strings String, booleans Boolean.
ConvertInputToAppFunctionDataUseCase.setArrayValue then hard-cast every array element to the
declared item type, so:

• a string-array parameter (e.g. message or contact IDs) crashed with
  ClassCastException: Long cannot be cast to String whenever Gemini sent numbers such as
  [101, 102];
• a boolean array failed on "true" / "false" strings;
• an unconvertible element surfaced as an opaque NumberFormatException: For input string: "abc"
  with no hint of which parameter was wrong.

The agent aborted the turn with "Failed to convert arguments for …".

The numeric branches already accept Number on main, but the remaining hard casts reported in #62
were still there: setStringList (it as String) and boolean arrays. Bad elements also still
produced errors with no context.

Solution

Array elements are now converted per item type through a single convertElements helper:

• string arrays: any non-null element via toString() (matches how scalar String params already work);
• int / long / double / float arrays: Number or a parseable String;
• boolean arrays: Boolean or "true"/"false" (case-insensitive);
• a null or unconvertible element, or a non-list value for an array parameter, fails with an
  IllegalArgumentException naming the parameter, element index and value, e.g.
  Parameter 'ints' expects an array of int, but element 1 is 'abc'.

The Gemini tool schema and the LLM payload are unchanged.

Evidence

Gemini-shaped JSON arguments run through toArgumentsMap() and the use case, before and after the fix:

Input	Before	After
{"messageIds": [101, 102, 3.5]} for a string array	ClassCastException: Long cannot be cast to String	["101", "102", "3.5"]
{"flags": ["true", false, "FALSE"]} for a boolean array	ClassCastException: String cannot be cast to Boolean	[true, false, false]
{"ints": [1, "2", 3.0], "longs": [9000000000, "4"]}	[1, 2, 3], [9000000000, 4]	unchanged
{"ints": [1, "abc"]}	NumberFormatException: For input string: "abc"	IllegalArgumentException: Parameter 'ints' expects an array of int, but element 1 is 'abc'

Testing

• Added 7 tests to ConvertInputToAppFunctionDataUseCaseTest: numbers in a string array, mixed
  numeric arrays (including the Double values JSON parsing produces), boolean strings, and
  failures for a bad element, a null element and a non-list value. Six of these fail on main.
• ./gradlew spotlessCheck :app:testStandardDebugUnitTest -PGEMINI_API_KEY=dummy_key: all pass.

Targets tested

agent app, standard flavor (JVM / Robolectric). The retail flavor uses the same code.

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