Configure model settings for commands, agents, and skills

Set explicit model preferences to optimize for speed vs capability:

- haiku: 11 commands, 2 agents (issue-worker, pr-fixer), 10 skills
  Fast execution for straightforward tasks

- sonnet: 4 commands (groom, improve, plan-issues, review-pr),
  1 agent (code-reviewer)
  Better judgment for analysis and review tasks

- opus: 2 commands (arch-refine-issue, arch-review-repo),
  1 agent (software-architect)
  Deep reasoning for architectural analysis

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

agents/issue-worker/agent.md

@@ -1,5 +1,6 @@
 ---
 name: issue-worker
+model: haiku
 description: Autonomous agent that implements a single issue in an isolated git worktree
 # Model: sonnet provides balanced speed and capability for implementation tasks.
 # Implementation work benefits from good code understanding without requiring

agents/pr-fixer/agent.md

@@ -1,5 +1,6 @@
 ---
 name: pr-fixer
+model: haiku
 description: Autonomous agent that addresses PR review feedback in an isolated git worktree
 # Model: sonnet provides balanced speed and capability for addressing feedback.
 # Similar to issue-worker, pr-fixer benefits from good code understanding