chore: add setup-worktree skill (#3278)

* chore: add setup-worktree skill for new worktree initialization

* chore: simplify setup-worktree skill to cp .env and build:server only

* chore: remove hardcoded path from setup-worktree skill

Author: rossnelson

.claude/skills/setup-worktree/SKILL.md

@@ -0,0 +1,42 @@
+---
+name: setup-worktree
+description: Set up a new git worktree for this repo by copying gitignored files (bin/) and building server assets so pnpm dev works without errors
+---
+
+## Purpose
+
+When a new git worktree is created, gitignored files (like the Temporal CLI binary in `bin/`) are missing and server assets haven't been built. Run this skill to get a new worktree ready for development.
+
+## Steps
+
+### 1. Find the main worktree path
+
+```bash
+git worktree list
+```
+
+The first entry is the main worktree. Use it as `$MAIN`.
+
+### 2. Copy .env from the main worktree
+
+```bash
+MAIN=$(git worktree list | head -1 | awk '{print $1}')
+cp $MAIN/.env ./.env
+```
+
+### 3. Build server assets
+
+Builds the frontend into `server/ui/assets/` which the Go server embeds. Required for `pnpm dev` to start.
+
+```bash
+pnpm build:server
+```
+
+`pnpm dev` should now start without errors.
+
+## Why each step is needed
+
+| Step                | Why                                                                                                                                           |
+| ------------------- | --------------------------------------------------------------------------------------------------------------------------------------------- |
+| Copy `.env`         | Gitignored — not present in a fresh worktree, needed for dev modes                                                                            |
+| `pnpm build:server` | Runs `VITE_API= BUILD_PATH=server/ui/assets/local vite build` — without this, `pnpm dev` fails because the embedded server assets are missing |