[codex] expand semantic layer coverage for macro signals

[C00ldudeNoonan]

Summary

• Expand MetricFlow semantic coverage for issue Expand semantic layer coverage: yield curve, financial conditions, sentiment, FOMC hawkish/dovish metrics #107 across treasury yield curve, financial conditions, FOMC sentiment, macro sentiment, net liquidity, diffusion, fiscal, and housing signals.
• Add user-facing simple metrics for yield spreads, financial stress, lending standards, FOMC hawkish/dovish/net sentiment, sentiment divergence, manufacturing indicators, liquidity, diffusion breadth, fiscal sustainability, and housing stress.
• Add tests and column documentation for agent_treasury_yield_curve_spreads so the yield curve semantic model has explicit grain and status constraints.

Why

Issue #107 identified existing warehouse models that were useful to agents but not yet exposed through the semantic layer. This makes those macro/market signals discoverable through dbt Platform and MetricFlow instead of requiring agents to know raw model names and SQL columns.

Validation

• uv run --project macro_agents dbt parse --project-dir dbt_project --profiles-dir dbt_project
• uv run --project macro_agents dbt ls --project-dir dbt_project --profiles-dir dbt_project --select agent_treasury_yield_curve_spreads financial_conditions_signals stg_fomc_sentiment_scores sentiment_signals net_liquidity_signals diffusion_index_signals fiscal_signals housing_signals
• uv run --project macro_agents dbt ls --project-dir dbt_project --profiles-dir dbt_project --resource-type semantic_model
• uv run --project macro_agents dbt ls --project-dir dbt_project --profiles-dir dbt_project --resource-type metric
• uv run --project macro_agents dbt build --project-dir dbt_project --profiles-dir dbt_project --select agent_treasury_yield_curve_spreads financial_conditions_signals stg_fomc_sentiment_scores sentiment_signals net_liquidity_signals diffusion_index_signals fiscal_signals housing_signals
• git diff --check

Warehouse-backed validation passed against BigQuery target prod: PASS=18 WARN=0 ERROR=0 SKIP=0 TOTAL=18. dbt registered 10 semantic models and 48 metrics.

Fixes #107

[C00ldudeNoonan]

@codex please review this PR.