Fix docstring formatting for Sphinx compatibility

- Make all attribute descriptions in IOModelOptions use consistent multi-line
  formatting to avoid RST definition list parsing issues
- Add docstrings to config model classes that were missing them, preventing
  inherited pydantic BaseModel docstrings (which use Markdown syntax) from
  being displayed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: robtaylor

chipflow/config/models.py

@@ -56,16 +56,23 @@ class SiliconConfig(BaseModel):
     # This is still kept around to allow forcing pad locations.
 
 class SimulationConfig(BaseModel):
+    """Configuration for simulation settings."""
     num_steps: int = 3000000
 
+
 class CompilerConfig(BaseModel):
+    """Configuration for compiler toolchain."""
     cpu: str
     abi: str
 
+
 class SoftwareConfig(BaseModel):
+    """Configuration for software build settings."""
     riscv: CompilerConfig = CompilerConfig(cpu="baseline_rv32-a-c-d", abi="ilp32")
 
+
 class TestConfig(BaseModel):
+    """Configuration for test settings."""
     event_reference: Path
 
 class ChipFlowConfig(BaseModel):

chipflow/platform/io/iosignature.py

@@ -66,12 +66,18 @@ class IOModelOptions(TypedDict):
         clock_domain: The name of the I/O's clock domain (see
             ``amaranth.hdl.ClockDomain``). NB there is only one of these, so IO
             with multiple clocks must be split up.
-        buffer_in: Should the IO pad have an input buffer?
-        buffer_out: Should the IO pad have an output buffer?
-        sky130_drive_mode: Drive mode for output buffer on sky130.
-        trip_point: Trip Point configuration for input buffer.
-        init: The value for the initial values of the port.
-        init_oe: The value for the initial values of the output enable(s) of the port.
+        buffer_in: Should the IO pad have an input buffer? Defaults to True for
+            ports with input direction.
+        buffer_out: Should the IO pad have an output buffer? Defaults to True for
+            ports with output direction.
+        sky130_drive_mode: Drive mode for output buffer on sky130. See
+            :class:`Sky130DriveMode` for available options.
+        trip_point: Trip Point configuration for input buffer. See
+            :class:`IOTripPoint` for available options.
+        init: The value for the initial values of the port. Can be an integer or
+            boolean.
+        init_oe: The value for the initial values of the output enable(s) of the
+            port. Can be an integer or boolean.
     """
 
     invert: NotRequired[bool|Tuple[bool, ...]]