fix: handle invalid script data after OP_RETURN in DecodeScript

[shruggr]

Summary

• Passes DecodeOptionsParseOpReturn to script.DecodeScript in xput.go so OP_RETURN data is parsed correctly
• Returns nil instead of propagating error when DecodeScript fails on unparseable output scripts (e.g. sCrypt contracts, non-standard OP_RETURN data)
• Bumps go-sdk from v1.1.27 to v1.2.18 (which introduced DecodeOptionsParseOpReturn)

Problem

Transaction 471442b27852e6a1a83e2f2bec8c1712ad3721534f2e35fda89b853471e7898f crashes the parsing pipeline. It contains an sCrypt contract output and a non-standard OP_RETURN output with invalid push data encoding. Without DecodeOptionsParseOpReturn, DecodeScript doesn't attempt to parse OP_RETURN data at all. With it enabled, when the post-OP_RETURN bytes can't be decoded, we now return nil so that:

1. The unparseable output still flows through with metadata (satoshis, address, index) but empty tapes
2. Other outputs in the same transaction parse normally
3. The entire transaction is not killed by one bad output

[mergify]

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[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 75.60%. Comparing base (447156f) to head (f45dc30).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
xput.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #96   +/-   ##
=======================================
  Coverage   75.60%   75.60%           
=======================================
  Files           3        3           
  Lines         287      287           
=======================================
  Hits          217      217           
  Misses         51       51           
  Partials       19       19           

Flag	Coverage Δ
unittests	75.60% <50.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
xput.go	78.28% <50.00%> (ø)

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