fix: avoid O(N) memory allocation when displaying large binary blobs in result panel

[kunwp1]

What changes were proposed in this PR?

When running a workflow that produces large binary fields (e.g. 50 MB blobs), the result panel appeared empty with no error messages. The root cause was that ExecutionResultService converted the entire byte array to a hex string (~3× the blob size in memory) before truncating it for display, causing the web server to take a very long time to fetch results.

The fix slices the byte array to only the bytes needed for the preview before encoding, making the conversion O(1) regardless of blob size. The display format is also updated from a hex dump (AB 12 CD...) to a binary string preview (<binary 0110100101...110, size = 52,428,800 bytes>), showing binaryPreviewLeadingBits (10) leading bits and binaryPreviewTrailingBits (3) trailing bits, just more clearly signaling opaque binary content.

Performance comparison (50 MB blob, averaged over 5 runs):

Approach	Time
Before (full hex conversion)	~5,971 ms
After (slice then encode)	~0.006 ms

~1,000,000× faster for a 50 MB blob; effectively constant time regardless of blob size.

Any related issues, documentation, discussions?

Closes #4875

How was this PR tested?

Test by running this workflow and check if the result appears almost immediately

Untitled workflow (11).json

Was this PR authored or co-authored using generative AI tooling?

Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.01%. Comparing base (33ea60e) to head (8fdde77).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4876      +/-   ##
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- Coverage     46.68%   44.01%   -2.68%     
- Complexity     2150     2151       +1     
============================================
  Files           843      957     +114     
  Lines         27322    34051    +6729     
  Branches       2533     3753    +1220     
============================================
+ Hits          12756    14986    +2230     
- Misses        13791    18312    +4521     
+ Partials        775      753      -22     

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[Yicong-Huang]

LGTM. One question inline.

[Yicong-Huang]

we had an offline discussion, the backend optimization is good.

but for frontend, maybe better to display non-HEX.

here is a suggested format:

<binary: abfas12312...adj 52,428,800 bytes>

[Yicong-Huang]

looks good!

[chenlica]

Great job!

[Yicong-Huang]

forgot to ask, does this need to be back ported to release/1.1?