Cover MAP parser validation and binary SELECT values

[rohenaz]

Follow up on #131’s uncovered parser branches. Add regression tests for malformed base64, absent cells, binary keys and commands, SELECT parameter validation, and exact binary-value preservation through SELECT SET/ADD/DELETE/REMOVE. Also verify unrelated protocol tapes remain ignored.

Validation: go test -race -coverprofile=coverage.out ./... passes. The parser package now has 100% statement coverage locally. This is Go statement coverage, not a prediction of Codecov’s branch/partial-line calculation. Production parser behavior is unchanged.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.27%. Comparing base (e100991) to head (aa8a661).

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #132       +/-   ##
===========================================
+ Coverage   59.72%   90.27%   +30.55%     
===========================================
  Files           4        4               
  Lines         144      144               
===========================================
+ Hits           86      130       +44     
+ Misses         40       14       -26     
+ Partials       18        0       -18     

Flag	Coverage Δ
unittests	90.27% <ø> (+30.55%)	⬆️

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see 3 files with indirect coverage changes

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