docs: add input-and-placement OpenSpec change and update AGENTS.md

Plan input handling and pattern placement before Game of Life mechanics:
keyboard bindings config, mouse placement with preview/rotation,
HiDPI scaling, and cell grid. Update AGENTS.md project notes.

openspec/config.yaml

@@ -0,0 +1,32 @@
+schema: spec-driven
+
+# Project context (optional)
+# Add only constraints that should guide OpenSpec artifacts and workflows.
+# Include constraints an agent cannot infer by reading the code.
+# Keep general project documentation and discoverable codebase facts out.
+# Example:
+#   context: |
+#     Designs and tasks must cover Windows, macOS, and Linux
+#     Write all artifacts in Spanish
+
+# Per-artifact rules (optional)
+# Add custom rules for specific artifacts.
+# Example:
+#   rules:
+#     proposal:
+#       - Keep proposals under 500 words
+#       - Always state what is out of scope
+#     tasks:
+#       - Break tasks into chunks of max 2 hours
+
+# Per-operation guidance (optional)
+# Add advisory guidance for how apply and archive work should be conducted.
+# This is separate from artifact rules above.
+# Example:
+#   operations:
+#     apply:
+#       guidance:
+#         - Keep test summaries concise
+#     archive:
+#       guidance:
+#         - Summarize the archive outcome before finishing