fix: add type specifiers to interpolated strings

[dbrattli]

Summary

Resolves all 127 GRA-INTERPOLATED-001 code-scanning alerts — "missing type specifiers in interpolated strings" — across 17 source files in Fable.Compiler and Fable.Transforms.

Each flagged interpolation hole gets the correct %-specifier so the type is checked at compile time. Output is unchanged; this only adds compile-time type safety:

• %s for strings (names, full names, formatted types, paths, error/warning messages) — the majority
• %d for ints (generated identifiers like arg{i}, FSharpChoice${n}, union tags, counters, arities)
• %O for objects whose default formatting already called ToString() (DateTime timestamps, Fable.Type, obj values, string option)

One site (FSharp2Fable.Util.fs) had a multi-line if/else inside the hole that went offside once the prefix widened, so it was hoisted into a small staticSuffix binding.

Verification

dotnet build src/Fable.Cli/Fable.Cli.fsproj -c Release succeeds with 0 warnings, 0 errors. The build itself is the safety net: a wrong specifier (%s on a non-string, %d on a non-int) is a hard compile error, so a clean build confirms every choice is type-correct. The identifier-generating strings (which feed into generated code, not just messages) produce byte-identical output, so there is no behavior change.

🤖 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

[dbrattli]

This should be safe since a wrong specifier should trigger a compile error. But touches many files, so please have a look and approve the PR if it looks OK with you @MangelMaxime @ncave