fix: flatten node_modules to resolve Windows path depth limit on bun install

Windows has a MAX_PATH limit of 260 characters. With deeply nested tscircuit
dependencies (poppygl → readable-stream → string_decoder → safe-buffer),
the nested node_modules structure exceeds this limit, causing ENOENT errors.

Solution: Set 'flatten = true' in [install] section of bunfig.toml to generate
a flattened node_modules structure, reducing path depth and avoiding Windows
MAX_PATH errors during 'bun install' on Windows runners.

Fixes: Windows Bun Tests failure - 'Failed to install 1 package'

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: 64johnlee

bunfig.toml

@@ -1,2 +1,6 @@
+[install]
+# Flatten node_modules to avoid Windows MAX_PATH (260 char) limit with deeply nested dependencies
+flatten = true
+
 [test]
 preload = ["tests/fixtures/preload.ts"]