feat(balance): capture metric projection evidence when due (ADC-686)

[wolf75222]

Scope

• publish the exact ConsumerGraph-derived automatic-balance due marker before Program operators
• capture signed before/after projection deltas in the qualified attempt mailbox
• use authenticated Cartesian/EB measures on Uniform and coverage-aware component-vector reductions on AMR
• preserve the marker in accepted-step rollback snapshots and fence the contract in source tests

Validation

• 28 focused Python tests passed; 3 unrelated Kokkos-dependent tests skipped because this source-only worktree has no Kokkos root configured
• Ruff passed
• serial/OpenMP System syntax-only compile passed
• MPICH/OpenMP AMR syntax-only compile passed
• documentation check passed with one pre-existing dependency freshness warning
• clang-format diff and git diff checks passed

Explicit nonclaims

This stack does not connect automatic evidence to accepted_balance_terms or a public BalanceLedger selector. Physical-boundary flux, source, and exact polar projection producers remain missing. It also does not replace the required native serial/MPI numerical acceptance run.

Stacked on #628. Tracks ADC-686.