docs: seed PRD + SPEC for the Go-direction rewrite

Two documents only — no Go code yet. PRD restates the problem and
preserves the Rust PRD's invariants verbatim, then maps the locked
stack to Go libraries and surfaces four hard problems (DuckDB-via-cgo
for the query engine, Lance dropped, Dioxus → HTMX, arrow-go maturity).
SPEC walks each Rust crate + TS surface and tags the port with library
choice / effort estimate / risk + a 5-phase migration plan from
skeleton (Phase G0) to demo parity (Phase G5).

Six open questions remain that gate Phase G0:
- DuckDB cgo OK?
- HTMX vs React for the UI?
- Repo location?
- Distillation v1.0.0 port verbatim or rebuild?
- Pathway memory data — port 88 traces or start clean?
- Auditor lineage — port audit_baselines.jsonl or restart?

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,41 @@
+# Go
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+*.test
+*.out
+go.work
+go.work.sum
+vendor/
+
+# Build artifacts
+/bin/
+/dist/
+
+# Editor / OS
+.DS_Store
+.idea/
+.vscode/
+*.swp
+*~
+
+# Local data — these directories follow the Rust lakehouse pattern;
+# regenerated by services on demand. Do not commit runtime artifacts.
+/data/_auditor/
+/data/_kb/
+/data/_pathway_memory/
+/data/_errors/
+/data/_imagecache/
+/data/datasets/
+/data/vectors/
+/data/headshots/
+/data/lance/
+/exports/
+/logs/
+/reports/
+
+# Secrets — never commit. Resolved via SecretsProvider per ADR-001 §1.x.
+*.env
+secrets.toml