Split out the `prek` tool usage instructions into a separate skill. This
should make the agent more likely to realize the skill is relevant to a
particular task and consult it. Extend the skill to include instructions
for using `prek` in a jj workspace, and add a helper script for that
situation.
Add a `jj` skill, with the main purpose being to instruct the agent to
use `jj` not `git`, and to use `--no-pager` when running it.
Extend the `bazel` tool description slightly to more strongly encourage
agents to read and follow it.
Assisted-by: Gemini via Antigravity
