docs: Phase A repo structure — archive, product, kebab-case

- Move copilot history and CSV to docs/archive/
- Add docs/product/ (SSP, intermediate, genre packs) and engineering/adrs/
- Rename all spaced/special-char doc paths to kebab-case
- Nest competitive GTM under docs/gtm/competitive/
- Point README and NORTH_STAR at CANONICAL_STRATEGY
- Leave code/ unchanged for later monorepo Phase B

docs/engineering/adrs/README.md

@@ -0,0 +1,26 @@
+# Architecture Decision Records (ADRs)
+
+Short, dated decisions so we do not re-litigate the same choices.
+
+## Format
+
+Each ADR: `NNNN-short-title.md`
+
+```markdown
+# NNNN — Title
+
+**Status:** proposed | accepted | superseded  
+**Date:** YYYY-MM-DD
+
+## Context
+## Decision
+## Consequences
+```
+
+## Index
+
+| ADR | Title | Status |
+|-----|-------|--------|
+| — | *(none yet)* | — |
+
+Candidates worth writing soon: HTTP vs stdio for production MCP; Cal.com orchestration vs rebuild booking; monorepo layout (Phase B).