Applies improved git permission restrictions to prevent workers from
corrupting the main /app repository. Extends protections beyond
implementation-worker to all agents with git bash access.
Introduce seven tier-selector pass-through agents (nano through opus, levels -2 to 4)
that enforce specific model tiers by forwarding prompts verbatim to a target agent.
Add implementation-supervisor, implementation-worker, and issue-estimator-util agents.
Standardize agent color conventions via comments across existing util and supervisor agents.
Replace the git-commit-helper agent with git-commit-util to align with
the existing naming convention (git-isolator-util). The new agent has a
fully rewritten specification including structured parameter tables,
environment variable fallbacks, explicit operation definitions, and
tightened permissions. All references in pr-merge-worker, supervisor,
and the list_prs_stale_conflicts README are updated accordingly.