docs(architecture): baseline current design (#109)

Capture the brownfield architecture and its relationship to the project vision.\n\n- add the current-state SAD and five retrospective ADRs\n- classify vision vectors against implementation evidence\n- record requirements, risks, gates, and construction handoff

.aiwg/requirements/UC-004.md

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+# UC-004 — Analyze a Source Code Repository
+
+**Primary actor:** Security researcher  
+**Goal:** Ingest supported source languages and identify evidence-backed vulnerability candidates.
+
+## Main Flow
+
+1. Researcher supplies an authorized repository.
+2. Ingest identifies language and extracts structural blocks.
+3. Decomposition and analysis produce candidate findings.
+4. Results are graded or verified against evidence.
+
+**Implementation coverage:** `src/recon/code-ingest.ts`, `src/recon/ts-parse.ts`, `src/recon/ts-grammars.ts`, `src/recon/whitebox.ts`, `src/analysis/`, decomposition scripts.
+
+**Maturity note:** Multi-language ingestion is experimental even where benchmark results are proven.