fix(patch): prevent invalid fuzzy match ranges

[amitksingh1490]

Summary

Fix incorrect range computation for fuzzy search matches in fs_patch and add bounds checking to prevent out-of-range replacements.

Context

Range::from_search_match previously derived byte offsets by assuming a single line-ending style across the entire file. That could produce incorrect ranges for content with mixed line endings, and downstream replacement logic could then attempt to index outside the source buffer.

Changes

• Reworked fuzzy-match range calculation to scan the source and use actual byte positions for each line
• Clamped start and end line indices to the valid file bounds
• Added an explicit RangeOutOfBounds error before slicing replacement ranges
• Added regression coverage for mixed line endings, trailing newlines, unicode content, and out-of-bounds matches

Key Implementation Details

The fix is centered in crates/forge_services/src/tool_services/fs_patch.rs, where range creation now tracks exact line start/end byte offsets instead of inferring offsets from a detected newline length. Replacement now validates the computed range before indexing into the source string.

Testing

cargo test -p forge_services fs_patch