fix: index single-line Kotlin objects - #1610

Approving — verified, though it took me a detour to do it correctly, and the detour is worth recording.

My first attempt said this PR was a no-op, because on my local venv main already handled single-line objects. That was wrong: my venv had tree-sitter-language-pack 0.13.0, while pyproject.toml pins >=1.6,<2.0. The behaviour here is entirely grammar-version dependent.

On the version the project actually pins (1.14.3), the reported misparse reproduces exactly:

object A { fun x() = 1 }   -> top-level node = infix_expression,  object_declaration captures = []
object A { }               -> top-level node = object_declaration, captures = ['A']
object A {\n  fun x()\n}   -> top-level node = object_declaration, captures = ['A']

So only the one-line-with-body form breaks, which is precisely what your infix_expression → (object_literal, simple_identifier, lambda_literal) shape match targets.

Re-running the comparison on grammar 1.14.3:

main:     objects=[Empty, MultiLine]            functions=[a→MultiLine, b→None,     c→Plain]
#1610:    objects=[Empty, OneLine, MultiLine]   functions=[a→MultiLine, b→OneLine,  c→Plain]

So it recovers both the missing Object node and the orphaned function's class_context — b was previously landing with no owner at all, which is the part that would quietly corrupt containment queries.

Guarding on the exact three-child shape and checking the first child's text is literally object is appropriately conservative — it won't misfire on genuine infix expressions.

tests/unit/parsers/test_kotlin_parser.py: 90 passed under grammar 1.14.3. Full unit suite: 1206 passed.

Thanks @mjq2020 — good fix, and it closes #1600.