[Repo Assist] Fix FormatException when #if directive appears between attribute lists in mutually recursive type

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Closes #3174

Root Cause

genOnelinerAttributes merged all AttributeListNodes into a single one-liner by collecting all attributes, taking the opening token from the first list and the closing token from the last. This silently dropped ContentBefore trivia (including #if/#endif directives) from all individual AttributeListNodes — only the outer MultipleAttributeListNode.ContentBefore was preserved via genNode n.

When NET5_0_OR_GREATER is defined, the Oak tree has two AttributeListNodes ([(Interface)] and [(Class)]) with the #endif directive stored in the second list's ContentBefore. The one-liner path dropped this directive, producing only 1 hash-fragment boundary instead of 2. The no-define variant (where both #if and #endif are on the outer node's ContentBefore) produced 2 boundaries. The mismatch caused mergeMultipleFormatResults to throw FormatException.

Fix

CodePrinter.fs — genOnelinerAttributes

Added detection: if any AttributeListNode at index ≥ 1 has a TriviaContent.Directive in its ContentBefore, fall back to rendering each list individually via genNode (which preserves per-list ContentBefore trivia). The lists are separated by sepNln and the last list is followed by sepSpace (not sepNln) so the type name follows on the same line.

CodePrinter.fs — genTypeDefn

Added directive detection for and type definitions. When attributes contain compiler directives, indent/unindent are forced around the attribute rendering and type name. This is required because attributes at column 0 after and\n are a parse error in F# — they must be indented. The indent also ensures that splitWhenHash (which uses TrimStart()) still detects the directives correctly, keeping fragment counts consistent across define variants.

Output

Input:

type X = int
and
#if NET5_0_OR_GREATER
    [(Interface)]
#endif
    [(Class)] Y = int

Formatted output (stable and idempotent):

type X = int

and
#if NET5_0_OR_GREATER
    [(Interface)]
#endif
    [(Class)] Y = int

Test Status

• ✅ Build succeeded (0 warnings, 0 errors)
• ✅ All 2738 tests pass (2737 existing + 1 new regression test)
• ✅ Output is idempotent (re-formatting produces identical result)
• ✅ Source code formatted with dotnet fantomas

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