feat: add us-cpa question engine

docs/us-cpa.md

@@ -17,6 +17,7 @@ Tax logic, case workflows, rendering, and review logic are still pending.
 
 ```bash
 skills/us-cpa/scripts/us-cpa question --question "What is the standard deduction?" --tax-year 2025
+skills/us-cpa/scripts/us-cpa question --question "What is the standard deduction?" --tax-year 2025 --style memo --format markdown
 skills/us-cpa/scripts/us-cpa prepare --tax-year 2025 --case-dir ~/tax-cases/2025-jane-doe
 skills/us-cpa/scripts/us-cpa review --tax-year 2025 --case-dir ~/tax-cases/2025-jane-doe
 skills/us-cpa/scripts/us-cpa fetch-year --tax-year 2025
@@ -98,9 +99,29 @@ Behavior:
 
 - JSON by default
 - markdown available with `--format markdown`
+- `question` supports:
+  - `--style conversation`
+  - `--style memo`
 - `question`, `prepare`, `review`, `extract-docs`, `render-forms`, and `export-efile-ready` still emit scaffold payloads with `status: "not_implemented"`
 - `fetch-year` emits a downloaded manifest location and source count
 
+## Question Engine
+
+Current `question` implementation:
+
+- loads the cached tax-year corpus
+- searches a small IRS-first topical rule set
+- returns one canonical analysis object
+- renders that analysis as:
+  - conversational output
+  - memo output
+- marks questions outside the current topical rule set as requiring primary-law escalation
+
+Current implemented topics:
+
+- standard deduction
+- Schedule C / sole proprietorship reporting trigger
+
 ## Scope Rules
 
 - U.S. federal individual returns only in v1