docs: add Apache 2.0 license and AI disclosure

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/ai-disclosure.md

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+# AI Disclosure
+
+This project was developed with assistance from Claude (Anthropic), an AI coding assistant.
+
+## How AI Was Used
+
+- **RTL design and debugging**: AI assisted with SystemVerilog implementation of the LDPC decoder core, Wishbone interface, and Caravel integration wrapper. AI-driven verification found and fixed 7 RTL bugs through standalone and vector-driven testbenches.
+- **Behavioral modeling**: Python simulation model (density evolution, BER analysis, test vector generation) co-developed with AI assistance.
+- **Build system and tooling**: OpenLane configuration, SDC timing constraints, and Makefile setup guided by AI.
+- **Documentation**: Architecture docs, project reports, and contest submission materials drafted with AI assistance.
+- **Design space exploration**: Code rate comparison, base matrix optimization, SC-LDPC analysis performed with AI-guided Python scripts.
+
+## Human Contributions
+
+All architectural decisions, algorithm selection (layered offset min-sum, QC-LDPC rate 1/8, IRA staircase structure), target application (photon-starved optical communication), and final design review were made by the human designer. The AI served as a coding assistant, technical reference, and verification tool.
+
+## Transparency
+
+Full conversation transcripts with the AI assistant are available upon request. Key AI-assisted files include:
+- `verilog/rtl/*.sv` — RTL implementation
+- `../model/*.py` — Python behavioral model (in parent ldpc_optical repo)
+- `openlane/*/config.json` — Synthesis configuration
+- `docs/` — Documentation
+
+## Tool
+
+- **AI Model**: Claude (Anthropic) via Claude Code CLI
+- **Usage Period**: February 2026