fix(metis): switch primary model to claude-sonnet-4-6 + correct AGENTS.md inaccuracies

Source code change:
- src/shared/model-requirements.ts: prepend claude-sonnet-4-6 to metis fallback
  chain so Sonnet becomes the default. Opus 4.7 max remains as the immediate
  fallback for callers who want extra reasoning.
- src/shared/model-requirements.test.ts: update assertion to expect Sonnet
  primary + Opus secondary.

AGENTS.md accuracy fixes (verified against source):
- Agent modes: Sisyphus/Hephaestus are 'primary' (not 'all'); Sisyphus-Junior
  is 'subagent' (not 'all'). Confirmed via 'const MODE: AgentMode = ...' in
  each agent file. Also clarified Prometheus has no agentSources factory and
  is built via buildPrometheusAgentConfig.
- Sisyphus fallback chain: corrected order to kimi-k2.6 → k2p5 → kimi-k2.5
  → gpt-5.5 medium → glm-5 → big-pickle (was missing kimi-k2.5).
- Librarian/Explore: added missing minimax-m2.7 step between -highspeed and
  claude-haiku-4-5.
- Metis chain: removed fictitious gemini-3.1-pro entry.
- Sisyphus-Junior chain: spelled out the actual fallback (was 'user-configurable').
- Temperatures: Sisyphus/Hephaestus do not set explicit temperature (model
  default); Sisyphus-Junior is 0.1 via SISYPHUS_JUNIOR_DEFAULTS.
- Quick category default: gpt-5.4-mini (not gpt-5.4-mini-fast).

Team-mode corrections:
- Eligibility registry has 3 verdicts: eligible (sisyphus, atlas, sisyphus-junior),
  conditional (hephaestus — needs D-36 teammate permission), hard-reject
  (oracle, librarian, explore, multimodal-looker, metis, momus, prometheus).
- Schema has 11 fields, not 4: added max_messages_per_run, max_wall_clock_minutes,
  max_member_turns, base_dir, message_payload_max_bytes, recipient_unread_max_bytes,
  mailbox_poll_interval_ms.
- Hooks: 'team-session-events' is 4 sub-handlers in src/plugin/event.ts
  (team-idle-wake-hint, team-lead-orphan-handler, team-member-error-handler,
  team-member-status-handler), not a single Continuation-tier hook.
- Tier counts now show base + team-mode: ToolGuard 14/15, Transform 5/7.
- Total: 52 base hooks, 59 with team-mode.

Doc cascade for the Metis change:
- docs/guide/orchestration.md, agent-model-matching.md, installation.md
- docs/reference/configuration.md, features.md

docs/reference/configuration.md

@@ -364,7 +364,7 @@ Capability data comes from provider runtime metadata first. OmO also ships bundl
 | **explore**           | `gpt-5.4-mini-fast` | `openai/gpt-5.4-mini-fast` → `opencode-go/qwen3.5-plus` → `vercel/minimax-m2.7-highspeed` → `opencode-go\|vercel/minimax-m2.7` → `anthropic\|opencode\|vercel/claude-haiku-4-5` → `openai\|opencode\|vercel/gpt-5.4-nano` |
 | **multimodal-looker** | `gpt-5.5`           | `openai\|opencode/gpt-5.5 (medium)` → `opencode-go/kimi-k2.6` → `zai-coding-plan/glm-4.6v` → `openai\|github-copilot\|opencode/gpt-5-nano` |
 | **Prometheus**        | `claude-opus-4-7`   | `anthropic\|github-copilot\|opencode/claude-opus-4-7 (max)` → `openai\|github-copilot\|opencode/gpt-5.5 (high)` → `opencode-go/glm-5.1` → `google\|github-copilot\|opencode/gemini-3.1-pro` |
-| **Metis**             | `claude-opus-4-7`   | `anthropic\|github-copilot\|opencode/claude-opus-4-7 (max)` → `openai\|github-copilot\|opencode/gpt-5.5 (high)` → `opencode-go/glm-5.1` → `kimi-for-coding/k2p5` |
+| **Metis**             | `claude-sonnet-4-6` | `anthropic\|github-copilot\|opencode/claude-sonnet-4-6` → `anthropic\|github-copilot\|opencode/claude-opus-4-7 (max)` → `openai\|github-copilot\|opencode/gpt-5.5 (high)` → `opencode-go/glm-5.1` → `kimi-for-coding/k2p5` |
 | **Momus**             | `gpt-5.5`           | `openai\|github-copilot\|opencode/gpt-5.5 (xhigh)` → `anthropic\|github-copilot\|opencode/claude-opus-4-7 (max)` → `google\|github-copilot\|opencode/gemini-3.1-pro (high)` → `opencode-go/glm-5.1` |
 | **Atlas**             | `claude-sonnet-4-6` | `anthropic\|github-copilot\|opencode/claude-sonnet-4-6` → `opencode-go/kimi-k2.6` → `openai\|github-copilot\|opencode/gpt-5.5 (medium)` → `opencode-go/minimax-m2.7` |