Phase 3: hygiene, dependencies, readme - #55

Issue #11 was disabled years ago because the CRC32 of some wav files
disagreed with StormLib's. A CRC32 over decoded content can only disagree if
the decode disagrees, so this settles it by decoding the same file twice.

tools/mpqcodecs.py implements Huffman and ADPCM transcribed from StormLib's
huff.cpp and adpcm.cpp -- from the C, not from the Java in this repository,
because an implementation that agrees by construction proves nothing. Both
now decode wavTest.w3x's ReviveNightElf.wav to the same 144464 bytes and the
same MD5. That file is the exact shape the issue thread described: sector 0
is plain zlib because it holds the RIFF header, and the other 34 sectors are
0x41, Huffman over ADPCM mono.

The committed golden manifest gains that digest, so GoldenFileTests now
checks the wav on every run rather than skipping it as undecodable.

IssueSampleTests covers the maps named in issues #46 and #47. They are other
people's maps so they are not committed; the tests skip unless pointed at a
directory with -PissueSamples. Forest Defense from #46 does open now, with
its declared header size of 2097410 repaired, and its files extract by name.

Coverage reporting is now continue-on-error. fail-on-error only covers the
upload, so a 504 from coveralls.io while the action fetched its own reporter
failed a job whose build, tests, reference checks and manifest check had all
passed. A reporting outage is not a broken build.

The writing example referenced Files, Path and StandardCharsets without
importing any of them, so it would not compile for the first person to copy
it. ReadmeExampleTests did not catch that, and could not: it runs the same
code with the imports on the test class, so it keeps the readme honest about
behaviour and says nothing about whether the text is copy-pasteable.

ReadmeSnippetCompilationTests compiles the text. Any block carrying at least
one import presents itself as complete and has to compile with only the
imports it declares; blocks with none are fragments that reference variables
the prose introduces, and are left alone. A floor on the number of complete
blocks found means the extraction cannot silently stop matching and start
verifying nothing.

Verified by reverting the readme to the flagged state: the test then names
Files, Path and StandardCharsets as missing. The rebuild example gained
imports and declarations for the same reason.