Add explicit model specifications to commands and agents

- Add model: sonnet to issue-worker agent (balanced for implementation)
- Add model: sonnet to pr-fixer agent (balanced for feedback iteration)
- Add model: haiku to /dashboard command (read-only display)
- Add model: haiku to /roadmap command (read-only categorization)
- Document rationale for each model selection in frontmatter comments

Closes #72

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

agents/issue-worker/agent.md

@@ -1,6 +1,10 @@
 ---
 name: issue-worker
 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
+# opus-level reasoning. Faster iteration through the implement-commit-review cycle.
+model: sonnet
 tools: Bash, Read, Write, Edit, Glob, Grep, TodoWrite
 skills: gitea, issue-writing, software-architecture
 ---

agents/pr-fixer/agent.md

@@ -1,6 +1,10 @@
 ---
 name: pr-fixer
 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
+# without requiring opus-level reasoning. Quick iteration on review feedback.
+model: sonnet
 tools: Bash, Read, Write, Edit, Glob, Grep, TodoWrite, Task
 skills: gitea, code-review
 ---

commands/dashboard.md

@@ -1,5 +1,8 @@
 ---
 description: Show dashboard of open issues, PRs awaiting review, and CI status.
+# Model: haiku is sufficient for fetching and displaying data.
+# This command only reads from Gitea and formats output - no complex reasoning needed.
+model: haiku
 ---
 
 # Repository Dashboard

commands/roadmap.md

@@ -1,5 +1,9 @@
 ---
 description: View current issues as a roadmap. Shows open issues organized by status and dependencies.
+# Model: haiku is sufficient for fetching and organizing issue data.
+# This command reads issues and dependencies, then displays them in categories.
+# Basic categorization logic doesn't require advanced reasoning.
+model: haiku
 argument-hint:
 ---