fix: use Terminal::text() for modifier text to avoid panic on malformed attribute args

[orizi]

Summary

Fixed text extraction for modifier tokens in attribute arguments by directly accessing the text from the specific modifier variant instead of using the generic syntax node method.

---

Type of change

Please check one:

• Bug fix (fixes incorrect behavior)
• New feature
• Performance improvement
• Documentation change with concrete technical impact
• Style, wording, formatting, or typo-only change

---

Why is this change needed?

The previous implementation used modifier.as_syntax_node().text(db) which could fail to extract text properly from modifier tokens in attribute arguments. This caused issues when processing attributes with modifier keywords like ref and mut.

---

What was the behavior or documentation before?

The Modifier::from method used a generic approach to extract text from modifier tokens by converting to a syntax node first, which was unreliable for certain modifier types.

---

What is the behavior or documentation after?

The method now pattern matches on the specific modifier variant (ast::Modifier::Ref or ast::Modifier::Mut) and calls the appropriate text() method directly, ensuring reliable text extraction for all modifier types.

---

Related issue or discussion (if any)

Fixes #9786

---

Additional context

The test case added demonstrates that attribute arguments with modifier keywords (like #[cfg(ref x)]) now parse correctly without generating diagnostics.

---

Note

Low Risk
Low risk bug fix in syntax attribute structuring that changes how ref/mut modifier text is read and adds a small regression test; no behavior changes outside malformed/edge-case parsing.

Overview
Fixes modifier text extraction for structured attribute arguments by reading ref/mut token text via the concrete ast::Modifier variants instead of as_syntax_node().text(db), preventing a potential panic on malformed attribute args.

Adds a semantic test case for an attribute argument containing a modifier keyword (#[cfg(ref x)]) to ensure it produces no diagnostics.

^{Written by Cursor Bugbot for commit a8da0fc. This will update automatically on new commits. Configure here.}

[reviewable-StarkWare]

This change is 

[orizi]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• fix: handle mismatched generic param kinds in substitution rewriter instead of panicking #9815
• fix: allow statement-level consts in named argument shorthand instead of panicking #9814
• fix: use Terminal::text() for modifier text to avoid panic on malformed attribute args #9813 👈 (View in Graphite)
• fix: handle missing struct field in const evaluation instead of panicking #9812
• fix: emit diagnostic for unsupported extern fn in const evaluation instead of panicking #9811
• fix: emit diagnostic for non-type numeric literal suffix instead of panicking #9810
• fix: return None for macro rule with missing param kind instead of panicking #9809
• fix: handle missing return type context in loop body instead of panicking #9808
• fix: emit diagnostic for member access on unreduced impl type instead of panicking #9807
• fix: emit diagnostic for unsupported items in statement position instead of panicking #9806
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[eytan-starkware]

@eytan-starkware reviewed 2 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on TomerStarkware).