Benchmark: keep pinned cases from reusing saved review sessions #628

Problem

Pinned benchmark cases reuse saved sessions. Neither the in-process executor (internal/cmd/benchmarkcmd/executor.go) nor reviewArgs (internal/cmd/benchmarkcmd/run.go) passes anything like --without-discussion (#627). So a pinned case resumes the PR's reviewer cohort and orchestrator session from any earlier run with the same profile and identity, and candidate B can inherit candidate A's reviewer selection and context.

Proposal

Add a per-case without_discussion setting to benchmark suites, defaulting to true for pinned cases, and pass it through both execution paths.