[fkjellberg]

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This PR separates reading the code lengths from building the tree, to prepare for replacing BinaryTree with the HuffmanDecoder in a follow-up PR.

Changes

• BinaryTree.decode(InputStream, int) is replaced by BinaryTree.fromCodeLengths(int[]). It builds the tree only from code lengths and checks that each length is in [1, 16].
• Reading the run-length encoded code lengths moves to ExplodingInputStream.readCodeLengths(...), with readBinaryTree(...) as a convenience wrapper.
• Variables renamed from "bit length" to "code length", and Javadoc added.

Fixes / behaviour changes

• Fixed the code length sort loop, which looped over the number of values instead of the possible code lengths.
• An encoded tree with fewer code lengths than expected (64 or 256) now throws ArchiveException. Before, the missing entries were silently ignored. This aligns with the implementation found in the Info-ZIP UnZip 6.0 utility.

Tests

• New unit tests for fromCodeLengths (valid, empty and out-of-range lengths) and for readCodeLengths (valid input, empty, truncated, too few and too many values).
• New end-to-end test for ExplodingInputStream that checks the decompressed output and the InputStreamStatistics counters.