chore(build): share target directory across agent worktrees

Add .cargo/config.toml to force all builds (including worktrees created
by Claude Code agents) to share a single target/ directory. Without this,
each worktree creates its own ~3GB target/ directory which fills the disk
when multiple agents are working in parallel.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.cargo/config.toml

@@ -0,0 +1,5 @@
+# Force all builds (including worktrees) to share one target directory.
+# This prevents each Claude Code agent worktree from creating its own
+# ~3GB target/ directory, which was filling the disk.
+[build]
+target-dir = "/Users/tayloreernisse/projects/gitlore/target"