Enforce strict Pyright gate

SLICE_HISTORY.md

@@ -1,5 +1,20 @@
 # Completed slices
 
+## DFG-15 strict static typing gate
+
+### Changed
+
+- Made the existing strict Pyright configuration resolve DocForge's `.venv` automatically.
+- Converted validated TOML, JSON, subprocess, socket, MCP, render, and visualization boundaries
+  from unknown dynamic values into explicit checked types.
+- Kept runtime validation and fail-closed behavior at every untrusted input boundary.
+- Made strict `pyright` an explicit repository development gate.
+
+### Verification
+
+- Pyright reports zero errors, warnings, or informational diagnostics across all source modules.
+- Ruff lint and formatting, Python compilation, all 52 warning-strict tests, and diff checks pass.
+
 ## DFG-14.1 detached viewer lifecycle correction
 
 ### Changed