Prepare and verify adopted bifurcation NetCDF candidate for MOI testing #237

Prepare and verify a separate six-region NetCDF collaborator candidate for MOI testing using the adopted conservative bifurcation FACC authority from #236.

Candidate: data/exports/v17c_beta/candidates/bifurcation_20261026_yushan_20261027/.

The build overlays adopted reach/node facc and facc_total onto copies of the existing 0.0.14 NetCDFs, adds reach head endpoints and adopted source/class fields, and preserves all other original values. The existing two headwater-neighbor repairs are present in the base. Legacy facc_flag and facc_quality values are retained and explicitly marked as inherited, not reassessed. The complete adopted total-area surface is installed; equality is to the frozen 21 October parent, not necessarily the older export.

Verification must independently reopen the outputs and check every non-overlay variable, exact ID-aligned adopted values, exact parent totals, node identity/order/dist_out, node interpolation, original topology and routing, reciprocal neighbor/count/acyclic/distance checks, frozen allocated-edge consistency, all 2,893 fork budgets, hashes and preserved inputs.

Completed: all six regions independently verified. Exact adopted values and parent totals pass for 248,673 reaches and 11,112,454 nodes; all 1,284 non-overlay variable arrays are preserved bit for bit. Node interpolation error is zero. All 2,893 fork allocations close with maximum residual 9.313225746154785e-10 km² and zero overbudget forks above 1 km². All 93 pinned inputs pass before/after hashes, and database metadata is unchanged. The run manifest and all 60 edge tables also match the original scientific source seal. Detailed results: VERIFICATION.json and FROZEN_INPUT_VERIFICATION.json. Six NetCDF files total 15.76 GB. Bundle includes reproducibility scripts, README, input/output manifests and checksums. This task does not email, upload or publish the files and does not open or modify a database. Source-placement/reference and direction follow-ups remain #233, #234 and #235.