ttl: establish phase-3 performance benchmark suite and optimization targets

[kdy1]

Summary

There is no benchmark suite or explicit optimization target contract to guide phase-3 performance work.

Evidence

Contract Evidence:

• docs/project-ttl.md:200
• docs/project-ttl-language.md:236

Current Gap

There is no benchmark suite or explicit optimization target contract to guide phase-3 performance work.

Proposed Scope

• Not documented yet.

Acceptance Criteria

• Add repeatable benchmark suite for key TTL compiler/runtime paths.
• Define baseline metrics and target thresholds for future optimization work.
• Provide guidance for regression detection and triage.
• Integrate benchmark execution into documented engineering workflow.

Test Scenarios

• Baseline benchmark run succeeds on representative TTL inputs.
• Regression comparison workflow identifies measurable slowdown.
• Benchmark harness remains stable across repeated runs.

Out of Scope

• Immediate optimization implementation for every hot path.
• Cross-repo benchmarking infrastructure.