chore: add git worktree docs and roborev configuration

.roborev.toml

@@ -0,0 +1,2 @@
+# roborev per-repo configuration
+agent = "claude-code"

CLAUDE.md

@@ -97,6 +97,52 @@ The Go CLI communicates the infrastructure path to Python Pulumi stacks via the
 
 - `just aws-unset`: Unset all AWS environment variables
 
+## Git Worktrees
+
+**Always use git worktrees instead of plain branches.** This enables concurrent Claude sessions in the same repo.
+
+### Creating a Worktree
+
+This repo is expected to live at `ptd-workspace/ptd/`. The `../../.worktrees/` relative path resolves to `ptd-workspace/.worktrees/` in that layout.
+
+```bash
+# New branch
+git worktree add ../../.worktrees/ptd-<branch-name> -b <branch-name>
+
+# Existing remote branch
+git worktree add ../../.worktrees/ptd-<branch-name> <branch-name>
+```
+
+Always prefix worktree directories with `ptd-` to avoid collisions with other repos.
+
+### After Creating a Worktree
+
+1. **Build the binary** — each worktree needs its own ptd binary:
+   ```bash
+   cd ../../.worktrees/ptd-<branch-name>
+   just build-cmd
+   ```
+2. **direnv** — if direnv is available, copy `envrc.recommended` to `.envrc` in the worktree, then run `direnv allow`. The file uses `source_up` to inherit workspace vars and overrides `PTD` to point to the worktree.
+3. **For agents without direnv** — set env vars explicitly before running `ptd` commands:
+   ```bash
+   export PTD="$(pwd)"
+   export PATH="${PTD}/.local/bin:${PATH}"
+   ```
+
+### Cleaning Up
+
+```bash
+# From the main checkout
+git worktree remove ../../.worktrees/ptd-<branch-name>
+```
+
+### Rules
+
+- **NEVER** use `git checkout -b` for new work — always `git worktree add`
+- **NEVER** put worktrees inside the repo directory — always use `../../.worktrees/ptd-<name>`
+- **ALWAYS** rebuild the binary after creating a worktree (`just build-cmd`)
+- Branch names: kebab-case, no slashes, no usernames (slashes break worktree directory paths)
+
 ## Contributing
 
 When contributing to the project:

envrc.recommended

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+# Inherit workspace-level environment (PTD_CONFIG, PTD_TARGETS_CONFIG_DIR, etc.)
+source_up
+
+# Override PTD to point to THIS directory (works for both main checkout and worktrees)
+export PTD="${PWD}"
+export PROJECT_ROOT="${PTD}"
+export TOP="${PTD}"
+export PTD_TOP="${PTD}"
+
+# Add this checkout's .local/bin to PATH (so worktrees use their own built binary)
+PATH_add ".local/bin"
+
+# Python/uv configuration for Pulumi operations
+export UV_PROJECT="${PTD}/python-pulumi"