feat(ui,infra): SvelteKit ui scaffold, Makefile, pre-commit, claude hooks

ui/: SvelteKit 2 + Svelte 5 + Tailwind 4 + shadcn-svelte (luma, lucide)
on bun with ultracite; adapter-static with SPA fallback; theme tokens
taken from msos. Dockerfile gains a bun stage that builds ui/build.
Makefile and pre-commit cover ruff, ty, ultracite and svelte-check;
.claude settings run the matching fixer after edits. docs/PRODUCT.md
captures product truth for the UI work.

.claude/CLAUDE.md

@@ -0,0 +1,22 @@
+## Code Principles
+- **Simplicity**: Write simple, straightforward code
+- **Readability**: Make code easy to understand
+- **Maintainability**: Write code that's easy to update
+- **Less Code = Less Debt**: Minimize code footprint
+- **NEVER write comments** - code should be self-documenting
+
+## Layout
+- `src/beaver_gateway` - python, unopinionated primitives (no vault paths, no agent names)
+- `ui` - SvelteKit SPA (admin + Obsidian panel), served by the gateway from `ui/build`
+- `docs/MISSION.md`, `docs/PRD.md`, `docs/PLAN.md`, `docs/PROGRESS.md` - keep PROGRESS.md current
+
+## Checking commands
+After writing code, always run (or `make check`):
+```shell
+ruff format          # python formatter
+ruff check --fix     # python linter
+ty check             # python type-checker
+cd ui && bun fix     # frontend linter+formatter (ultracite)
+cd ui && bun check   # svelte-check
+```
+Dependencies: `uv add` / `cd ui && bun add`, never edit lock files by hand.