refactor(python): add ty suppression codes to existing type: ignores

[dbrattli]

Summary

Five library lines carry intentional # type: ignore[<code>] comments for Pyright — genuine, accepted typing gaps:

• int32.div_rem — // / % on a deliberately weak SupportsInt bound (# type: ignore[operator])
• StringableBase.__str__/__repr__ — duck-typed self.ToString() provided by subclasses (# type: ignore[attr-defined])
• FSharpArray.append — intentional LSP-incompatible override of MutableSequence.append (# type: ignore[override])
• async_.parallel — map(...) arg-type (# type: ignore[arg-type])

ty does not honour mypy/pyright rule codes, so it re-reported all of these. This appends ty-prefixed suppressions as a separate trailing comment:

q = x // y  # type: ignore[operator]  # ty: ignore[unsupported-operator]

Why the separate-comment form

Folding the ty code into the same bracket — # type: ignore[operator, ty:unsupported-operator] — breaks Pyright's bracket parser (the : invalidates the whole comment) and de-suppresses the line. With two comments, Pyright reads its [...] bracket and ty reads # ty: ignore[...]. Verified against Pyright 1.1.407 and latest with the repo's reportUnnecessaryTypeIgnoreComment: true config.

Verification

	ty (lib)	ty (tests)	Pyright (lib)	Pyright (tests)	runtime
before	68	118	0	34	2350 ✓
after	61	118	0	34	2350 ✓

Silences 7 false/intentional ty diagnostics with no change to Pyright and all 2350 Python tests passing. (Counts are relative to current main, i.e. after #4637 and #4638.)

Context

Part of an investigation into whether ty could eventually replace Pyright for this repo. Together with #4638 (FSharpRef overloads, −178) this brings ty from 364 → 179 total diagnostics. The remainder are genuine ty solver limitations (Option/SomeWrapper typevar widening, bidirectional generic specialization) best left until ty matures.

🤖 Generated with Claude Code

[github-actions]

Python Type Checking Results (Pyright)

Metric	Value
Total errors	34
Files with errors	4
Excluded files	4
New errors	✅ No

Excluded files with errors (4 files)

These files have known type errors and are excluded from CI. Remove from pyrightconfig.ci.json as errors are fixed.

File	Errors	Status
temp/tests/Python/test_hash_set.py	18	Excluded
temp/tests/Python/test_applicative.py	12	Excluded
temp/tests/Python/test_nested_and_recursive_pattern.py	2	Excluded
temp/tests/Python/fable_modules/thoth_json_python/encode.py	2	Excluded