Add trace-density region cost option

[seveibar]

What changed

• Add an opt-in TRACE_DENSITY_COST_FACTOR solver option.
• Penalize quadratic trace occupancy normalized by available layer count and region area.
• Preserve legacy behavior with a default factor of zero.
• Add coverage for density scaling, layer capacity, and the unchanged default.

Why

The existing region cost can be zero for many parallel traces even when concentrating those traces makes downstream detailed routing expensive. This option lets callers evaluate a capacity-aware global-routing candidate without changing the default policy.

Validation

• bun run typecheck
• 20 focused tiny-hypergraph tests covering region cost, outside-in partial rip, selective rerip, distance-aware routing, and compact candidate storage
• git diff --check

The paired autorouter PR uses this option behind a guarded candidate portfolio and benchmarks it against main on the same machine.

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Project	Deployment	Actions	Updated (UTC)
tiny-hypergraph	Ready	Preview	Aug 12, 2026 11:11pm

[tscircuitbot]

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/benchmark [benchmark.sh args...]
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Everything after /benchmark is forwarded directly to ./benchmark.sh.
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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

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