docs(adcp): document git worktree isolation pattern for parallel agents (#428)

* docs(adcp): add parallel agent isolation (git worktree) section to CLAUDE.md

Documents the git worktree pattern for parallel agent isolation, including
spawn checklist, .env and pre-commit setup steps, teardown, and branch
naming convention. Closes #418.

https://claude.ai/code/session_017TUh8WYUoUWzdxDQMPLM5t

* fixup: use git-common-dir for .env copy; add CONDUCTOR.md cross-link

Addresses pre-PR review blockers: replace unresolvable /path/to/repo-root
placeholder with git rev-parse --git-common-dir to reliably locate the
main worktree root, and add CONDUCTOR.md cross-reference.

https://claude.ai/code/session_017TUh8WYUoUWzdxDQMPLM5t

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: bokelley

CLAUDE.md

@@ -149,6 +149,42 @@ pytest tests/ -v          # Tests
 
 All three must pass. CI runs them across Python 3.10–3.13; locally running on your current version catches most issues.
 
+## Parallel Agent Isolation (git worktrees)
+
+When multiple agents work in the same checkout simultaneously, they clobber each other's
+branches — there is no error, the work is silently lost. Use `git worktree` to give each
+agent an isolated checkout.
+
+> **Note:** Conductor worktrees handle this automatically via `.conductor.json`
+> (runs `setup_conductor_env.py` + `pre-commit install` on create). Use the
+> manual steps below only for raw `git worktree` outside of Conductor.
+> See `CONDUCTOR.md` for Conductor-specific setup and troubleshooting.
+
+**Create a worktree:**
+
+```bash
+git worktree add /tmp/claude-issue-<N>-<slug> -b claude/issue-<N>-<slug> main
+```
+
+**Setup checklist (run inside the new worktree):**
+
+```bash
+cd /tmp/claude-issue-<N>-<slug>
+cp "$(git rev-parse --git-common-dir)/../.env" .env   # .env is not inherited
+pre-commit install                 # hooks are not inherited from parent worktree
+pip install -e .[dev]              # install in this worktree's context
+```
+
+**Teardown (after branch is merged):**
+
+```bash
+git worktree remove /tmp/claude-issue-<N>-<slug>
+# or: git worktree prune   # removes all stale worktrees at once
+```
+
+**Branch naming:** always follow `claude/issue-<N>-<short-slug>` — branch-protection
+rules enforce this pattern and PRs from non-conforming names may be rejected.
+
 ## Additional Important Reminders
 
 **NEVER**: