Add isolated post-solve unravel region optimizer

[seveibar]

Summary

• add UnravelTinyHyperGraphSolver, a post-solve optimizer that untwists boundary assignments and reroutes/ejects routes while monotonically improving the solved graph's existing region-cost objective
• run the optimizer as the final stage of the core TinyHyperGraphSectionPipelineSolver
• add exact whole-graph validation, layer/via and terminal-clearance safety checks, route-path reuse, and focused unit coverage
• report P50/P95 before/after costs from the immediate pre-unravel stage so the benchmark attributes only the new step

This supersedes #166 for review. Unlike that reference PR, this branch is based directly on main and contains no region-cost-model, trace-density, Poly/Pipeline9, geometric-connectivity, or simpleRouteJson changes.

Isolated benchmark

./benchmark.sh on all eight committed SRJ18 Pipeline7 cases, comparing optimizeSection directly to optimizeRegionCosts:

Metric	Before	After	Reduction
P50 max region cost	1.440	0.541	62.4%
P95 max region cost	3.464	1.496	56.8%

• solved-route completion: 100%
• cases improved: 8/8
• average optimizer time: 3.281s

Validation

• bun test — 135 pass, 0 fail
• bun run typecheck
• bun run format:check — pass (existing oversized-fixture warning only)
• git diff --check

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Project	Deployment	Actions	Updated (UTC)
tiny-hypergraph	Ready	Preview	Aug 15, 2026 7:03pm

[tscircuitbot]

Benchmark This PR

Run benchmarks by commenting on this PR:

/benchmark [benchmark.sh args...]
/benchmark --dataset <hg07|srj18> --limit <n> --solver <core|poly> --families <default|default+deep|all> --concurrency <n|auto>

Everything after /benchmark is forwarded directly to ./benchmark.sh.
Every command runs current main and the PR head sequentially on the same Blacksmith machine, then reports their results side by side.

Examples:

• /benchmark -> all committed completed SRJ18 Pipeline7 cases, core solver
• /benchmark --limit 4 -> first four committed Pipeline7 cases
• /benchmark --dataset srj18 --concurrency auto -> srj18 samples with runner CPU-count concurrency
• /benchmark --sample sample003 -> one committed SRJ18 Pipeline7 case
• /benchmark --dataset hg07 --limit 20 --solver poly -> first 20 hg07 samples with the poly solver
• /benchmark --dataset hg07 --limit 40 --families default+deep -> first 40 hg07 samples with deeper candidate families

Any PR whose title contains [BENCHMARK TEST] will automatically run the benchmark workflow on PR updates.