feat: Nonfiction Intake System - All Three Paths

This commit completes Issue #18 (Purpose Classifier), adds Intake Agent
and CLI integration:

1. PURPOSE CLASSIFIER (Issue #18 - DONE earlier)
   - Keyword-based classification into 6 ReaderPurposes
   - LLM-enhanced classification for nuanced cases

2. INTAKE AGENT (NEW - addresses Issue #20, #23)
   - Created opus_orchestrator/nonfiction/intake.py
   - Intelligent agent that combines:
     * Explicit flags (--purpose, --category)
     * Keyword classification (auto-detect)
     * Conversational questions (when ambiguous)
   - IntakeAgent class with process() method
   - determine_intake() convenience function
   - get_questions() for conversational mode
   - Source tracking: explicit | classifier | intake | hybrid

3. CLI INTEGRATION (Issue #23)
   - Added --purpose flag: learn, understand, transform, decide, reference, inspire
   - Added --category flag: business, leadership, memoir, etc.
   - Both passed to orchestrator

Usage:
  # Explicit
  opus generate --book-type nonfiction --purpose transform --category self_help

  # Auto-classify
  opus generate --book-type nonfiction --concept "How to build a startup"

  # Programmatic
  result = await determine_intake(
    concept="Leadership for introverts",
    purpose="transform",  # or None for auto
    category="leadership",
    mode="auto"  # or "conversational"
  )

opus_orchestrator/cli.py

@@ -82,6 +82,9 @@ class OpusAPIClient:
         tone: str = "literary",
         use_crewai: bool = False,
         use_autogen: bool = True,
+        # Nonfiction options
+        purpose: str = None,
+        category: str = None,
     ) -> dict:
         """Generate a manuscript.
         
@@ -108,6 +111,8 @@ class OpusAPIClient:
             "chapters": chapters,
             "tone": tone,
             "use_crewai": use_crewai,
+            "purpose": purpose,
+            "category": category,
         }
         
         if concept:
@@ -234,6 +239,17 @@ Examples:
         choices=["fiction", "nonfiction"],
         help="Book type",
     )
+    # Nonfiction-specific options
+    gen_parser.add_argument(
+        "--purpose",
+        choices=["learn", "understand", "transform", "decide", "reference", "inspire"],
+        help="Reader purpose (nonfiction): learn (hands-on), understand (concepts), transform (change), decide (choose), reference (manual), inspire (motivation)",
+    )
+    gen_parser.add_argument(
+        "--category",
+        choices=["business", "leadership", "entrepreneurship", "self_help", "memoir", "philosophy", "science", "history", "technology", "finance", "health", "relationships", "creativity", "spirituality", "how_to"],
+        help="Nonfiction category (optional): business, leadership, memoir, etc.",
+    )
     gen_parser.add_argument(
         "--words", "-w",
         type=int,
@@ -548,6 +564,8 @@ async def run_generate(args: argparse.Namespace) -> int:
                 tone=args.tone,
                 use_crewai=args.use_crewai,
                 use_autogen=not args.no_autogen,
+                purpose=args.purpose,
+                category=args.category,
             )
             
             print(f"✅ Generation complete!")