fix: use ${COPILOT_PLUGIN_ROOT} in hooks.json to fix cwd crash

[kwacky1]

Problem

preToolUse hooks crash with preToolUse hook errored whenever the session cwd is anywhere other than the plugin directory. This blocks every tool call in sessions launched with --tickets or any other flag that bundles the-power.

Repro (verified 2026-07-05): Launch any Copilot CLI session from an unrelated repo (e.g. si-clops) with the plugin active. Every tool call returns preToolUse hook errored.

Root cause: hooks.json used "cwd": "." (commit 538bcac) then "cwd": "${PLUGIN_ROOT}" (commit 1f7a3d7 — partial fix), plus a relative "bash": "./hooks/guard-*.sh". The runtime resolves . against session cwd, not the plugin dir. With a relative bash path, the script is never found.

# Reproduces the failure:
cd ~/some-project
echo '{"tool_name":"bash","tool_input":{"command":"echo hello"}}' | bash ./hooks/guard-destructive-ops.sh
# bash: ./hooks/guard-destructive-ops.sh: No such file or directory — exit 127

Fix

Move the absolute path into the bash field using ${COPILOT_PLUGIN_ROOT} — the token the Copilot CLI runtime injects for the plugin install directory. Remove the cwd field entirely (no longer needed).

Evidence of runtime support: config_loader_expand_plugin_hook_config, config_loader_expand_plugin_root_in_object, and the literal ${COPILOT_PLUGIN_ROOT} / ${PLUGIN_ROOT} strings are all present in the Copilot CLI runtime.node native module (v1.0.69-1). The si-clops plugin uses the same pattern and works correctly.

{
  "type": "command",
  "bash": "${COPILOT_PLUGIN_ROOT}/hooks/guard-destructive-ops.sh",
  "timeoutSec": 10
}

Changes

• copilot-plugin/hooks.json — use ${COPILOT_PLUGIN_ROOT}/hooks/... in bash field; remove cwd field
• copilot-plugin/tests/test-guardrails.sh — run test suite from a temporary directory (not the plugin dir) to catch future regressions; 4 new cwd-independence test cases
• copilot-plugin/README.md — document the fix and add 'Testing hooks locally' section

Testing

bash copilot-plugin/tests/test-guardrails.sh
# 39 tests: 39 passed, 0 failed

The test suite now cd's to a temp dir before running, so all 39 tests exercise hooks from a foreign cwd.

Related

Fixes #579 (part of the same safety hook neighbourhood)
Related: PR #580 (fail-open behaviour)