Enhance ADB-S to ADB-D business cases

docs/business-case-flow.md

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+# Business Case Flow
+
+Option 8 produces an executive business-case deck plus reusable YAML backing
+data. For ADB-S to ADB-D cases, use `business_case.adbs_to_adbd`.
+
+## ADB-S to ADB-D Rules
+
+- Keep workload/billable ECPU demand comparable between ADB-S and ADB-D unless
+  the customer provides a different target demand.
+- Dedicated physical capacity is a separate fixed footprint:
+  `DB nodes x ECPU per DB node`.
+- Never model ADB-D at 100% utilization by default. Show utilization explicitly.
+- ADB-D fixed infrastructure includes DB servers and storage servers; workload
+  ECPU demand remains a separate line.
+- Projected BOMs are annual run-rate snapshots at the horizon, not cumulative
+  multi-year totals.
+- GoldenGate can be `steady_state`, `migration_bridge_only`, or
+  `migration_plus_fallback_months`. Bridge-only GoldenGate is excluded from
+  future steady-state BOMs.
+
+## Read Architecture
+
+ADB-S and ADB-D can carry the same workload demand while using different read
+architectures. ADB-S may require refreshable/read clones when standby is not the
+application read path. ADB-D may use Local ADG read-only standby and retire
+steady-state clones. The deck should call this out in BOM notes, value drivers,
+and risk/value slides.
+
+## Storage Economics
+
+Storage economics are shown separately from aggregate TCO:
+
+```text
+break-even TB = fixed dedicated infra monthly cost / ADB-S storage USD per GB-month / 1024
+```
+
+Apply discounts uniformly when comparing scenarios. If customer material
+provides a baseline break-even, show it beside the recalculated break-even for
+the proposed footprint.
+
+## Business Value
+
+Risk-reduction cases use a Business Value Model instead of generic ROI
+percentages. Do not invent revenue impact. Convert stability to USD only when
+the customer provides revenue-at-risk, transaction margin, fraud loss impact, or
+cost per degraded/outage hour.
+
+Use:
+
+```text
+avoided degraded/outage hours x business impact per hour
+```
+
+Track success metrics such as CPU utilization, read latency, clone lag retired,
+ADG read lag, GoldenGate/apply lag during migration, incidents avoided, and
+degraded hours avoided.
+
+## Validation
+
+Business-case deck validation reads text boxes, table cells, and grouped shapes.
+It checks expected titles, disclaimer-last, required assumptions, and forbidden
+obsolete phrases such as `OCI Annual`, stale scenario risks, and unclear
+language like `FTE-year`.