feat: add us-cpa case intake workflow

docs/us-cpa.md

@@ -20,7 +20,7 @@ skills/us-cpa/scripts/us-cpa question --question "What is the standard deduction
 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
-skills/us-cpa/scripts/us-cpa extract-docs --tax-year 2025 --case-dir ~/tax-cases/2025-jane-doe
+skills/us-cpa/scripts/us-cpa extract-docs --tax-year 2025 --case-dir ~/tax-cases/2025-jane-doe --create-case --case-label "Jane Doe" --facts-json ./facts.json
 skills/us-cpa/scripts/us-cpa render-forms --tax-year 2025 --case-dir ~/tax-cases/2025-jane-doe
 skills/us-cpa/scripts/us-cpa export-efile-ready --tax-year 2025 --case-dir ~/tax-cases/2025-jane-doe
 ```
@@ -71,6 +71,29 @@ Current `fetch-year` bootstrap corpus for tax year `2025` is verified against li
   sources/
 ```
 
+Current implementation writes:
+
+- `case-manifest.json`
+- `extracted/facts.json`
+- `issues/open-issues.json`
+
+## Intake Flow
+
+Current `extract-docs` supports:
+
+- `--create-case`
+- `--case-label`
+- `--facts-json <path>`
+- repeated `--input-file <path>`
+
+Behavior:
+
+- creates the full case directory layout when `--create-case` is used
+- copies input documents into `input/`
+- stores normalized user-statement facts in `extracted/facts.json`
+- appends document registry entries to `case-manifest.json`
+- stops with a structured issue and non-zero exit if a new fact conflicts with an existing stored fact
+
 ## Output Contract
 
 - JSON by default