feat(bench): add comprehensive throughput analysis tool

Add new `bench_throughput` binary for detailed performance analysis of
string_pipeline operations at scale. This tool is designed to analyze
performance for real-world usage patterns, particularly for the
television TUI project.

Features:
- 28+ comprehensive templates covering all operations
- Real-world path processing templates (filename extraction, etc.)
- Per-operation timing breakdown with --detailed flag
- Latency statistics (min, p50, p95, p99, max, stddev)
- JSON output format for tracking performance over time
- Scaling analysis (sub-linear, linear, super-linear detection)
- Operation-level metrics (call counts, time attribution)
- Throughput measurements (paths/sec)
- Parse cost analysis across input sizes

Template Categories:
- Core operations: split, join, upper, lower, trim, replace, etc.
- Path operations: extract filename, directory, extension, basename
- Complex chains: multi-operation pipelines
- Map operations: nested transformations

CLI Options:
- --sizes: Comma-separated input sizes (default: 100-100K)
- --iterations: Measurement iterations for stability
- --detailed: Enable operation profiling and statistics
- --format: Output format (console or json)
- --output: JSON output file path

Performance Targets:
- File browser (50K paths): < 100ms total, > 500K paths/sec
- Search results (10K paths): < 20ms total
- Process list (1K paths): < 2ms total

Documentation:
- docs/bench_throughput_plan.md: Comprehensive enhancement plan
- docs/bench_throughput_usage.md: Usage guide with examples
- test_bench_throughput.sh: End-to-end test script

This tool enables:
1. Identifying performance bottlenecks
2. Measuring optimization impact
3. Tracking performance regressions
4. Validating scaling behavior
5. Real-world workload analysis for television integration

Author: claude

Cargo.toml

@@ -38,6 +38,11 @@ path = "src/main.rs"
 name = "string-pipeline-bench"
 path = "src/bin/bench.rs"
 
+[[bin]]
+bench = false
+name = "bench_throughput"
+path = "src/bin/bench_throughput.rs"
+
 [profile.staging]
 inherits = "dev"
 opt-level = 3