Initial scaffold: tooling, plan, task briefs

- pnpm 10 workspace + TypeScript strict + ESLint flat + Prettier
- CLAUDE.md as canonical brief
- docs/tasks/ — 22 task briefs broken out by phase for sub-sessions
- docs/decisions/ — ADR scaffold

Implements task 01 (repo-init).

docs/decisions/README.md

@@ -0,0 +1,25 @@
+# Architecture decisions
+
+Lightweight ADRs. Add one only when a non-obvious choice is made and the reasoning would be hard to reconstruct later. Keep each under ~300 words.
+
+## Format
+
+```
+# NNNN — Title
+
+Date: YYYY-MM-DD
+Status: accepted | superseded by NNNN
+
+## Context
+What problem we faced.
+
+## Decision
+What we chose.
+
+## Consequences
+What this costs us, what it buys us.
+```
+
+## Index
+
+- (none yet — add as decisions are made)