refactor(engine): pass Python worker startup arguments by name

[yangzhang75]

What changes were proposed in this PR?

Passes Python worker startup configuration by name instead of by argv position, as proposed in the issue.

PythonWorkflowWorker (JVM) previously built ~19 positional command-line arguments, and texera_run_python_worker.py unpacked them positionally. Because the two sides agreed only by index, adding/removing/reordering one argument could silently misassign values.

• PythonWorkflowWorker.scala: build a single JSON object of named startup-config keys and pass it as one argument.
• texera_run_python_worker.py: parse that JSON and read each value by key; a missing or renamed key now raises a clear KeyError instead of silently misaligning.

The set of keys written on the Scala side and read on the Python side is identical (19 keys). No behavior change otherwise.

Any related issues, documentation, discussions?

Closes #5547

How was this PR tested?

• Verified the JSON key set written by PythonWorkflowWorker.scala exactly matches the keys read in texera_run_python_worker.py (19 keys, no drift).
• WorkflowExecutionService/compile (amber) succeeds.
• scalafmtCheckAll passes; scalafix rules (RemoveUnused, ProcedureSyntax) are satisfied (the new import is used).
• Python entry script passes py_compile.
• End-to-end worker launch is exercised by the existing CI integration jobs (amber-integration), which start a real Python worker.

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

Generated-by: Claude Code (Claude Opus 4.8)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 29 lines in your changes missing coverage. Please review.
✅ Project coverage is 52.36%. Comparing base (07ca5d4) to head (1e6d0ca).

Files with missing lines	Patch %	Lines
...chitecture/pythonworker/PythonWorkflowWorker.scala	0.00%	25 Missing ⚠️
amber/src/main/python/texera_run_python_worker.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5597      +/-   ##
============================================
- Coverage     52.38%   52.36%   -0.03%     
+ Complexity     2484     2481       -3     
============================================
  Files          1070     1070              
  Lines         41359    41367       +8     
  Branches       4441     4441              
============================================
- Hits          21666    21661       -5     
- Misses        18427    18438      +11     
- Partials       1266     1268       +2     

Flag	Coverage Δ		*Carryforward flag
access-control-service	64.61% <ø> (ø)		Carriedforward from 07ca5d4
agent-service	33.76% <ø> (ø)		Carriedforward from 07ca5d4
amber	53.26% <0.00%> (-0.06%)	⬇️
computing-unit-managing-service	1.65% <ø> (ø)		Carriedforward from 07ca5d4
config-service	56.06% <ø> (ø)		Carriedforward from 07ca5d4
file-service	38.21% <ø> (ø)		Carriedforward from 07ca5d4
frontend	46.91% <ø> (ø)		Carriedforward from 07ca5d4
pyamber	90.62% <0.00%> (-0.10%)	⬇️
python	90.80% <ø> (+0.04%)	⬆️	Carriedforward from 07ca5d4
workflow-compiling-service	58.69% <ø> (ø)		Carriedforward from 07ca5d4

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

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[xuang7]

Could you assign a reviewer for this PR? @chenlica