Initial commit: Lush vs Bash AI benchmarking framework

Benchmark harness that uses LLM agents to solve shell scripting tasks
in both Bash and Lush, then compares correctness and code quality.

- CLI with run, run-all, list-tasks, report, and export commands
- Agent loop with retry support via Anthropic Claude provider
- Test harness executing solutions in sandboxed subprocesses
- LLM-driven questionnaire for subjective code quality evaluation
- HTML report export with charts (matplotlib)
- 8 Category A tasks (write-from-scratch in both languages)
- 4 Category B tasks (verify provided Bash, convert to Lush)
- Lush language reference for agent context

tasks/category_a/two_sum.toml

@@ -0,0 +1,24 @@
+name = "two_sum"
+category = "a"
+description = """
+Read input from stdin. The first line contains a target integer.
+The second line contains space-separated integers (the array).
+Find two indices (0-based) such that the numbers at those indices add up to the target.
+Print the two indices on a single line, space-separated, smaller index first.
+There is exactly one solution.
+"""
+
+[[test_cases]]
+stdin = """9
+2 7 11 15"""
+expected_stdout = "0 1"
+
+[[test_cases]]
+stdin = """6
+3 2 4"""
+expected_stdout = "1 2"
+
+[[test_cases]]
+stdin = """6
+3 3"""
+expected_stdout = "0 1"