feat(gui): export a workflow as Python, and read the schema's constraints in the panel

[kz930]

What changes were proposed in this PR?

Everything the browser side of this work needs, in one piece.

A button on the workflow toolbar asks the compiling service to translate the canvas into a Python script and shows what comes back, with a copy control so the script can be taken somewhere that runs it. The translation is a round trip, so the button disables itself while one is in flight, and a workflow the translator cannot express comes back with a reason rather than an empty modal. The route is added in the two places a browser reaches the compiling service from: the dev server's proxy and the single-node nginx.

A workflow that fails to compile cannot be executed either, so the run button reads the compilation state alongside the schema and port validation it already read. Running to one operator is offered only when everything upstream of it compiled too, not only the operator itself.

The property panel reads the constraints the schema declares. A column property is checked against the attribute type rule for every column it names rather than only the first. A hyperparameter's value renders as the control its parameter implies: a dropdown where the accepted set is known, a number input where it is numeric, a plain text box where the rules say nothing.

Any related issues, documentation, discussions?

Part of #8325, 21 of 21; that issue lists the set in order.

This one stands alone. It touches no Scala, so it compiles and its tests run on their own, and its CI is green today. The endpoint the button calls is added in #8327: until that lands, clicking it reports that the request failed and nothing else changes, so the order here is a preference rather than a constraint.

Supersedes #7983, #7980 and the frontend half of #7946, which are closed in favour of this. They touched the same three files, so reviewing them apart meant reading the same code more than once and resolving a conflict between them at merge.

Closes #7981. Part of #7979, #7952 and #7936, whose remaining half is in #8348; those three stay open until both land, since each is only fixed once the schema declares the rule and the panel enforces it.

Closes #8427, the task this change is the whole of.

How was this PR tested?

The five affected specs pass at 447 tests. They cover the three ways the export click can end, the run button and the execute-to-here entry under a failed compilation, a column property that names several columns, and each control the value rules select.

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

Generated-by: Claude Code (Opus 5)

[github-actions]

Automated Reviewer Suggestions

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

• Contributors with relevant context: @PG1204, @tanishqgandhi1908, @ELin2025
  You can notify them by mentioning @PG1204, @tanishqgandhi1908, @ELin2025 in a comment.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.12422% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.06%. Comparing base (7976744) to head (dd463c2).

Files with missing lines	Patch %	Lines
...src/app/workspace/component/menu/menu.component.ts	53.33%	13 Missing and 1 partial ⚠️
...c/app/workspace/component/menu/menu.component.html	41.66%	7 Missing ⚠️
...it-frame/operator-property-edit-frame.component.ts	86.11%	2 Missing and 3 partials ⚠️
frontend/src/app/common/formly/formly-utils.ts	95.83%	0 Missing and 2 partials ⚠️
...r/workflow-to-python/workflow-to-python.service.ts	71.42%	2 Missing ⚠️
...t/constrained-value/constrained-value.component.ts	90.47%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8350      +/-   ##
============================================
- Coverage     94.11%   94.06%   -0.05%     
  Complexity     4811     4811              
============================================
  Files          1197     1199       +2     
  Lines         48813    48953     +140     
  Branches       5906     5942      +36     
============================================
+ Hits          45939    46047     +108     
- Misses         1420     1446      +26     
- Partials       1454     1460       +6     

Flag	Coverage Δ		*Carryforward flag
access-control-service	81.00% <ø> (ø)		Carriedforward from 91ed19e
agent-service	99.32% <ø> (ø)		Carriedforward from 91ed19e
amber	90.08% <ø> (ø)		Carriedforward from 91ed19e
computing-unit-managing-service	73.67% <ø> (ø)		Carriedforward from 91ed19e
config-service	87.00% <ø> (ø)		Carriedforward from 91ed19e
file-service	87.91% <ø> (ø)		Carriedforward from 91ed19e
frontend	96.74% <80.12%> (-0.13%)	⬇️
notebook-migration-service	79.31% <ø> (ø)		Carriedforward from 91ed19e
pyamber	98.47% <ø> (ø)		Carriedforward from 91ed19e
workflow-compiling-service	77.19% <ø> (ø)		Carriedforward from 91ed19e

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

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[kz930]

/request-review @mengw15

[kz930]

@carloea2 May you take a look at it?

[carloea2]

Please add before and after screenshots for the new toolbar button and modal. Also list the exact frontend test command. This changes visible UI, and the current test section only gives a test count.