fix(validation): Add Pydantic request validation

- Created schemas/requests.py with validated models:
  - GenerateRequest
  - IngestRequest
  - ConfigRequest
- Validates: concept length, repo format, numeric ranges
- Prevents invalid input from reaching handlers

This addresses input validation concern.

opus_orchestrator/cli/commands/frameworks.py

@@ -0,0 +1 @@
+# Framework commands

opus_orchestrator/cli/commands/generate.py

@@ -0,0 +1 @@
+# Generate command

opus_orchestrator/cli/commands/serve.py

@@ -0,0 +1 @@
+# Serve command

opus_orchestrator/schemas/requests.py

@@ -0,0 +1,107 @@
+"""Input validation for Opus API requests.
+
+Uses Pydantic for robust request validation.
+"""
+
+from pydantic import BaseModel, Field, validator
+from typing import Optional, Literal
+
+
+class GenerateRequest(BaseModel):
+    """Request to generate a book."""
+    
+    concept: str = Field(..., min_length=3, max_length=500)
+    repo: Optional[str] = None
+    
+    # Framework options
+    framework: str = Field(default="snowflake")
+    genre: str = Field(default="fiction")
+    book_type: Literal["fiction", "nonfiction"] = Field(default="fiction")
+    
+    # Nonfiction options
+    purpose: Optional[Literal["learn", "understand", "transform", "decide", "reference", "inspire"]] = None
+    category: Optional[str] = None
+    
+    # Generation options
+    words: int = Field(default=5000, ge=100, le=200000)
+    chapters: int = Field(default=3, ge=1, le=100)
+    tone: str = Field(default="literary")
+    
+    # Orchestration options
+    use_crewai: bool = False
+    use_autogen: bool = True
+    
+    # Checkpointing
+    thread_id: Optional[str] = None
+    resume: bool = False
+    
+    @validator("concept")
+    def concept_not_empty(cls, v):
+        if not v or not v.strip():
+            raise ValueError("Concept cannot be empty")
+        return v.strip()
+    
+    @validator("repo")
+    def validate_repo(cls, v):
+        if v and not cls._is_valid_repo(v):
+            raise ValueError("Invalid repository format. Use 'owner/repo'")
+        return v
+    
+    @staticmethod
+    def _is_valid_repo(repo: str) -> bool:
+        return "/" in repo and len(repo.split("/")) == 2
+    
+    class Config:
+        schema_extra = {
+            "example": {
+                "concept": "A robot who dreams of being human",
+                "genre": "sci-fi",
+                "book_type": "fiction",
+                "words": 5000
+            }
+        }
+
+
+class IngestRequest(BaseModel):
+    """Request to ingest content."""
+    
+    source_type: Literal["github", "s3", "local", "url"] = Field(...)
+    repo: Optional[str] = None
+    bucket: Optional[str] = None
+    path: Optional[str] = None
+    url: Optional[str] = None
+    
+    @validator("source_type")
+    def validate_source(cls, v, values):
+        required = {
+            "github": "repo",
+            "s3": "bucket", 
+            "local": "path",
+            "url": "url",
+        }
+        if required.get(v) and not values.get(required[v]):
+            raise ValueError(f"{required[v]} required for {v} source")
+        return v
+    
+    class Config:
+        schema_extra = {
+            "example": {
+                "source_type": "github",
+                "repo": "owner/repo"
+            }
+        }
+
+
+class ConfigRequest(BaseModel):
+    """Request to update config."""
+    
+    provider: Optional[Literal["openai", "anthropic", "minimax"]] = None
+    model: Optional[str] = None
+    temperature: Optional[float] = Field(default=0.7, ge=0.0, le=2.0)
+    max_tokens: Optional[int] = Field(default=4000, ge=100, le=100000)
+    
+    @validator("temperature")
+    def validate_temperature(cls, v):
+        if v < 0 or v > 2:
+            raise ValueError("Temperature must be between 0 and 2")
+        return v