Fix nondeterministic concurrency in PointCommand

[progys]

Problem

`PointCommand` performed its work in a parallel stream via a mutable `AreaConsumer` that accumulated `totalArea` and printed each matching shape from inside `accept()`, which runs on worker threads. Consequences:

• Shape lines were printed in nondeterministic order across runs.
• The `totalArea` float sum order varied run to run.

Fix

• The parallel stream now only computes matches: `parallelStream().filter(shape.inShape(point)).toList()` — no shared mutable state, and `toList()` preserves encounter order.
• Printing and the area summation happen afterwards in a single sequential loop, so output ordering and the float result are deterministic.

Verification

• New `PointCommandTest` (2 cases): encounter-order + combined area output, and empty-result path. Full suite now 11/11 green.
• End-to-end: two runs of a parallel point query produce byte-identical output (same hash).

[cursor]

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