simplify: remove dead code in seq_subset and delete gmon.out

- seq_subset.cpp: Remove redundant 'e ⊆ a*' check (lines 46-48).
  When a=epsilon and b=b1*, get_info(b1*).nullable is always l_true,
  so the earlier epsilon+nullable check already handles this case.

- seq_subset.cpp: Remove redundant 'R ⊆ R*' check (lines 50-52).
  The preceding 'a ⊆ a*' check uses the same is_star condition but
  calls is_subset_rec with the same depth (more budget), making the
  depth+1 variant unreachable in any useful scenario.

- seq_subset.cpp: Remove trailing whitespace (lines 22, 33).

- Remove accidentally committed gmon.out profiling output file.

- .gitignore: Add gmon.out to prevent future accidental commits.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.gitignore

@@ -124,3 +124,5 @@ bazel-*
 .deeptest/
 tptp_test/
 tptp_benchmarks/
+# Profiling output files
+gmon.out