feat: update default model to Claude Opus 4.6

[bjpl]

Summary

Updates the default Claude model across the codebase from claude-opus-4-5-20251101 to claude-opus-4-6.

Relates to #1082

What changed (17 files, 25 lines)

Category	Files	Changes
Settings	.claude/settings.json, .claude/settings copy.json	Default model → claude-opus-4-6, customInstructions text
CLI settings	v3/@claude-flow/cli/.claude/settings.json, v3/@claude-flow/mcp/.claude/settings.json	Default model config
Settings generator	v3/@claude-flow/cli/src/init/settings-generator.ts	Generated model string
Provider registry	v3/@claude-flow/plugins/src/providers/index.ts	Model ID in provider list
Statusline	v3/@claude-flow/cli/src/init/statusline-generator.ts, v3/@claude-flow/cli/.claude/helpers/statusline.js, v3/@claude-flow/mcp/.claude/helpers/statusline.js	Display name → Opus 4.6
Hooks	v3/@claude-flow/cli/src/commands/hooks.ts, v3/@claude-flow/hooks/src/statusline/index.ts	Hardcoded model display name
Git helpers	.claude/helpers/auto-commit.sh, v3/@claude-flow/cli/.claude/helpers/auto-commit.sh, v3/@claude-flow/mcp/.claude/helpers/auto-commit.sh	Co-author tag
Safety hooks	v3/@claude-flow/shared/src/hooks/safety/git-commit.ts	Model name string
Documentation	README.md, v3/@claude-flow/cli/README.md	Banner, provider table, statusline example

Why

Claude Opus 4.6 shipped Feb 5, 2026 with:

• Effort levels (low/medium/high/max) — GA, no beta header needed
• Adaptive thinking — replaces budget_tokens (deprecated)
• 128K max output (doubled from 64K)
• 1M context window (beta)
• Compaction API (beta) — server-side context summarization
• Simplified model ID — claude-opus-4-6 (no date suffix)
• Same pricing — $5/$25 per MTok

Breaking change awareness

• Assistant message prefilling is not supported on Opus 4.6 (returns 400)
• budget_tokens in thinking config is deprecated (still works for now)
• interleaved-thinking beta header is deprecated (safely ignored)

Verification

# No remaining opus-4-5 references outside CHANGELOG
grep -rn "claude-opus-4-5" --include="*.ts" --include="*.js" --include="*.json" --include="*.md" . | grep -v node_modules | grep -v CHANGELOG
# → 0 results

# No remaining "Opus 4.5" display names
grep -rn "Opus 4\.5" --include="*.ts" --include="*.js" --include="*.json" --include="*.md" . | grep -v node_modules | grep -v CHANGELOG
# → 0 results

Testing checklist

• npx @claude-flow/cli@latest init --wizard generates claude-opus-4-6 in settings
• Statusline displays Opus 4.6
• hooks model-route returns updated model name
• No remaining references to claude-opus-4-5 outside CHANGELOG
• Build passes with no regressions