refactor(workflow-operator): extract shared Sklearn descriptor base

[Ma77Ball]

What changes were proposed in this PR?

• Add abstract SklearnModelOpDesc extends PythonOperatorDescriptor holding the four shared config fields (target, countVectorizer, text, tfidfTransformer) with their Jackson/JSON-schema annotations, the two @JsonIgnore hooks (getImportStatements, getUserFriendlyModelName), and the shared getOutputSchemas.
• Change SklearnClassifierOpDesc and SklearnTrainingOpDesc to extend the new base, so each keeps only what genuinely differs (generatePythonCode, operatorInfo), removing ~50 lines of copy-pasted, drift-prone code.
• The 51 leaf subclasses inherit the fields unchanged, so the generated operator schema is identical (no behavior change).

Any related issues, documentation, discussions?

Closes: #6038

How was this PR tested?

• Pure refactor with no behavior change; covered by existing SklearnOpDescRegistrySpec, which instantiates a leaf classifier, sets the inherited target/countVectorizer fields, and asserts on generatePythonCode() output. Run it in CI via sbt "WorkflowOperator/jacoco", expect the Sklearn registry specs green.
• Verified locally with sbt "WorkflowOperator/Test/compile" (compiles clean; both descriptors resolve against SklearnModelOpDesc).
• Note: sbt "WorkflowOperator/testOnly *SklearnOpDescRegistrySpec" could not run locally because sbt-jacoco offline-instruments the Test classpath and JaCoCo 0.8.11 fails to instrument the vendored JsonSchemaDraft.class on this JDK (pre-existing tooling issue, unrelated to this change); the spec runs in CI under the WorkflowOperator/jacoco job.

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

Co-authored with Claude Opus 4.8 in compliance with ASF

[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @aglinxinyuan, @carloea2
  You can notify them by mentioning @aglinxinyuan, @carloea2 in a comment.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.63%. Comparing base (24b587f) to head (406b2ef).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...ber/operator/sklearn/SklearnClassifierOpDesc.scala	33.33%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6048      +/-   ##
============================================
- Coverage     56.89%   56.63%   -0.27%     
- Complexity     3058     3059       +1     
============================================
  Files          1129     1127       -2     
  Lines         43802    43326     -476     
  Branches       4743     4669      -74     
============================================
- Hits          24922    24536     -386     
+ Misses        17449    17392      -57     
+ Partials       1431     1398      -33     

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)
agent-service	44.59% <ø> (ø)		Carriedforward from 16a3ddf
amber	58.66% <86.66%> (+0.01%)	⬆️
computing-unit-managing-service	0.00% <ø> (ø)
config-service	52.30% <ø> (ø)
file-service	62.81% <ø> (ø)
frontend	49.39% <ø> (-0.74%)	⬇️	Carriedforward from 16a3ddf
notebook-migration-service	78.57% <ø> (ø)
pyamber	90.51% <ø> (-0.64%)	⬇️	Carriedforward from 16a3ddf
python	90.69% <ø> (ø)		Carriedforward from 16a3ddf
workflow-compiling-service	55.14% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.

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[github-actions]

⚠️ Benchmark changes need a look

🟢 2 better · 🔴 6 worse · ⚪ 7 noise (<±5%) · 0 without baseline

Compared against main 24b587f benchmarked on this same runner, so the delta is largely free of cross-runner hardware noise. The "7d avg" column still reflects the gh-pages dashboard. Treat <±5% as noise unless repeated.

Dashboard · Run

	config	throughput	MB/s	latency	max Δ latest / 7d
🔴	bs=10 sw=10 sl=64	365	0.222	25,474/44,057/44,057 us	🔴 +19.3% / 🔴 +188.2%
🔴	bs=100 sw=10 sl=64	777	0.474	129,690/142,726/142,726 us	🔴 +6.9% / 🔴 +31.7%
⚪	bs=1000 sw=10 sl=64	915	0.559	1,087,055/1,144,885/1,144,885 us	⚪ within ±5% / 🔴 +10.4%

Baseline details

Latest main 24b587f from same runner

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	365 tuples/sec	405 tuples/sec	770.95 tuples/sec	-9.9%	-52.7%
bs=10 sw=10 sl=64	MB/s	0.222 MB/s	0.247 MB/s	0.471 MB/s	-10.1%	-52.8%
bs=10 sw=10 sl=64	p50	25,474 us	23,027 us	12,775 us	+10.6%	+99.4%
bs=10 sw=10 sl=64	p95	44,057 us	36,915 us	15,286 us	+19.3%	+188.2%
bs=10 sw=10 sl=64	p99	44,057 us	36,915 us	18,795 us	+19.3%	+134.4%
bs=100 sw=10 sl=64	throughput	777 tuples/sec	805 tuples/sec	976.93 tuples/sec	-3.5%	-20.5%
bs=100 sw=10 sl=64	MB/s	0.474 MB/s	0.492 MB/s	0.596 MB/s	-3.7%	-20.5%
bs=100 sw=10 sl=64	p50	129,690 us	121,325 us	102,557 us	+6.9%	+26.5%
bs=100 sw=10 sl=64	p95	142,726 us	153,232 us	108,383 us	-6.9%	+31.7%
bs=100 sw=10 sl=64	p99	142,726 us	153,232 us	115,249 us	-6.9%	+23.8%
bs=1000 sw=10 sl=64	throughput	915 tuples/sec	921 tuples/sec	1,009 tuples/sec	-0.7%	-9.3%
bs=1000 sw=10 sl=64	MB/s	0.559 MB/s	0.562 MB/s	0.616 MB/s	-0.5%	-9.2%
bs=1000 sw=10 sl=64	p50	1,087,055 us	1,083,681 us	997,695 us	+0.3%	+9.0%
bs=1000 sw=10 sl=64	p95	1,144,885 us	1,119,007 us	1,036,731 us	+2.3%	+10.4%
bs=1000 sw=10 sl=64	p99	1,144,885 us	1,119,007 us	1,069,334 us	+2.3%	+7.1%

Raw CSV

config_idx,batch_size,schema_width,string_len,num_batches,total_ms,total_tuples,total_bytes,tuples_per_sec,mb_per_sec,lat_p50_us,lat_p95_us,lat_p99_us
0,10,10,64,20,548.65,200,128000,365,0.222,25473.54,44056.63,44056.63
1,100,10,64,20,2575.62,2000,1280000,777,0.474,129689.60,142726.00,142726.00
2,1000,10,64,20,21855.82,20000,12800000,915,0.559,1087054.65,1144884.51,1144884.51

[aglinxinyuan]

This string should be empty since it gets overridden anyway. The placeholder was introduced by mistake in the first place.

[aglinxinyuan]

ditto