## What does this PR do?
Fixes#22003 by escaping tab characters in filenames when generating
sourcemap JSON.
When a filename contained a tab character (e.g., `file\ttab.js`), the
sourcemap JSON would contain a **literal tab byte** instead of the
escaped `\t`, producing invalid JSON that caused `error:
InvalidSourceMap`.
The root cause was in `src/bun.js/bindings/highway_strings.cpp` where
the scalar fallback path had:
```cpp
if (char_ >= 127 || (char_ < 0x20 && char_ != 0x09) || ...)
```
This **exempted tab characters** (0x09) from being detected as needing
escape, while the SIMD path correctly detected them. The fix removes the
`&& char_ != 0x09` exemption so both paths consistently escape tabs.
## How did you verify your code works?
Added regression test in `test/regression/issue/22003.test.ts` that:
- Creates a file with a tab character in its filename
- Builds it with sourcemap generation
- Verifies the sourcemap is valid JSON
- Checks that the tab is escaped as `\t` (not a literal byte)
The test **fails on system bun** (produces invalid JSON with literal
tab):
```bash
USE_SYSTEM_BUN=1 bun test test/regression/issue/22003.test.ts
# error: JSON Parse error: Unterminated string
```
The test **passes with the fix** (tab properly escaped):
```bash
bun bd test test/regression/issue/22003.test.ts
# ✓ 1 pass
```
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
