fix(add-noqa): preserve trailing content after noqa directives

[sergioperezcheco]

Summary

When running --add-noqa on a line with an existing noqa directive that has trailing content (e.g. a trailing reason or a # fmt:skip comment), the edit was extending to the end of the line and overwriting that trailing content.

Reproduction

import math  # noqa: RUF100 with a trailing reason
import sys  # noqa: RUF100 # fmt:skip

Before (broken):

import math  # noqa: F401, RUF100
import sys  # noqa: F401, RUF100

Both the trailing reason and # fmt:skip are deleted.

After (fixed):

import math  # noqa: F401, RUF100 with a trailing reason
import sys  # noqa: F401, RUF100 # fmt:skip

Trailing content is preserved.

Root Cause

In generate_noqa_edit (crates/ruff_linter/src/noqa.rs), the Directive::Codes branch computed edit_range as TextRange::new(TextSize::of(trimmed_line), line_range.len()), which extends from the end of the trimmed code to the end of the full line. This range includes any trailing content after the noqa directive.

Fix

1. Limit the edit range for Directive::Codes to only cover up to existing_codes.end() — the end of the noqa directive itself — leaving trailing content untouched.
2. Add an emit_line_ending: bool flag to NoqaEdit so the line ending is only emitted when the edit actually covers the end of the line (the None / blank-line case).

Test Plan

Added add_noqa_existing_noqa_with_trailing_content test verifying both scenarios (trailing reason and # fmt:skip). All 14 existing add_noqa tests continue to pass.

test lint::add_noqa ... ok
test lint::add_noqa_existing_noqa ... ok
test lint::add_noqa_existing_noqa_with_trailing_content ... ok   ← new
... (14 passed, 0 failed)

Closes #26287