Fix CBO income source PE-native loss units

[MaxGhenis]

Summary

• classify national CBO income-by-source targets as dollar targets before generic filer/count handling
• add a regression test for the CBO self-employment and interest/non-qualified dividend targets that drove the Fix rent and childcare export inputs #190 APG tradeoff
• preserve IRS count targets as return-count targets

Why

The #190 release-candidate APG comparison won headline robust national loss but regressed important IRS/investment-income surfaces. The top improvement/regression diagnostics showed CBO income_by_source/.../filers targets with dollar-scale targets (for example self-employment income and taxable-interest plus non-qualified dividends) were being bucketed as national:returns because the path ended with filers. That misbucketing distorts the robust loss objective and the release gate.

Tests

• uv run --python 3.13 --project /Users/maxghenis/.codex-worktrees/microplex-us-fix-cbo-income-unit-20260602 --extra dev python -m pytest /Users/maxghenis/.codex-worktrees/microplex-us-fix-cbo-income-unit-20260602/tests/pipelines/test_pe_native_loss.py
• uv run --python 3.13 --project /Users/maxghenis/.codex-worktrees/microplex-us-fix-cbo-income-unit-20260602 ruff check /Users/maxghenis/.codex-worktrees/microplex-us-fix-cbo-income-unit-20260602/src/microplex_us/pipelines/pe_native_loss.py /Users/maxghenis/.codex-worktrees/microplex-us-fix-cbo-income-unit-20260602/tests/pipelines/test_pe_native_loss.py