chore: fix goboscript file formatter

[kabugatti]

📝 Fix multi-line %define formatter alignment and loop issue

🛠️ Issue

• Closes Fix goboscript files formatter #180

📖 Description

• Rewrite the format_buffer_inplace function in src/fmt.rs to correctly handle multi-line preprocessor directives (%define ... \).
• Ensure only true multi-line directives (lines that start with % and end with \) are processed, preventing an infinite loop on single-line directives.
• Improve trimming and spacing logic to align backslashes at column 88 without corrupting content.
• Rebuild the buffer after processing to maintain integrity and avoid in-place index errors.

✅ Changes made

• Updated the main loop to only enter the formatting block when line.starts_with(b"%") && line.ends_with(b"\\").
• Added logic to collect all consecutive continuation lines into a directive_lines vector, then trim trailing spaces and insert the correct number of spaces before each backslash.
• Ensured the index i advances past the entire directive block, preventing infinite loops and hangs.
• Rebuilt the entire src buffer at the end by concatenating modified lines, ensuring safe byte-level operations.
• Retained existing error handling (FmtError) and file read/write patterns.

📜 Additional Notes

• Manual and automated tests were run against tests/formatter and existing test suites to confirm no regressions.
• The formatter now exits cleanly and aligns backslashes correctly for all tested cases.
• Future improvements could include extending formatting support beyond preprocessor directives and integrating more Goboscript style rules.

[aspizu]

slop