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/guide/agent-model-matching.md

@@ -205,7 +205,7 @@ These agents have Claude-optimized prompts — long, detailed, mechanics-driven.
 | Agent | Role | Fallback Chain |
 |---|---|---|
 | **Sisyphus** | Main orchestrator | `anthropic\|github-copilot\|opencode\|vercel/claude-opus-4-7` (max) → `opencode-go\|vercel/kimi-k2.6` → `kimi-for-coding/k2p5` → `opencode\|moonshotai\|moonshotai-cn\|firmware\|ollama-cloud\|aihubmix\|vercel/kimi-k2.5` → `openai\|github-copilot\|opencode\|vercel/gpt-5.5` (medium) → `zai-coding-plan\|opencode\|vercel/glm-5` → `opencode/big-pickle` |
-| **Metis** | Plan gap analyzer | `anthropic\|github-copilot\|opencode\|vercel/claude-opus-4-7` (max) → `openai\|github-copilot\|opencode\|vercel/gpt-5.5` (high) → `opencode-go\|vercel/glm-5.1` → `kimi-for-coding/k2p5` |
+| **Metis** | Plan gap analyzer | `anthropic\|github-copilot\|opencode\|vercel/claude-sonnet-4-6` → `anthropic\|github-copilot\|opencode\|vercel/claude-opus-4-7` (max) → `openai\|github-copilot\|opencode\|vercel/gpt-5.5` (high) → `opencode-go\|vercel/glm-5.1` → `kimi-for-coding/k2p5` |
 
 ### Dual-Prompt Agents → Claude preferred, GPT supported
 

docs/guide/installation.md

@@ -335,7 +335,7 @@ Based on your subscriptions, here's how the agents were configured:
 | Agent        | Role             | Default Chain                                   | What It Does                                                                             |
 | ------------ | ---------------- | ----------------------------------------------- | ---------------------------------------------------------------------------------------- |
 | **Sisyphus** | Main ultraworker | anthropic\|github-copilot\|opencode/claude-opus-4-7 (max) → opencode-go/kimi-k2.6 → kimi-for-coding/k2p5 → opencode\|moonshotai\|moonshotai-cn\|firmware\|ollama-cloud\|aihubmix/kimi-k2.5 → openai\|github-copilot\|opencode/gpt-5.5 (medium) → zai-coding-plan\|opencode/glm-5 → opencode/big-pickle | Primary coding agent. Exact runtime chain from `src/shared/model-requirements.ts`. |
-| **Metis**    | Plan review      | 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 | Reviews Prometheus plans for gaps. Exact runtime chain from `src/shared/model-requirements.ts`. |
+| **Metis**    | Plan review      | 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 | Reviews Prometheus plans for gaps. Exact runtime chain from `src/shared/model-requirements.ts`. |
 
 **Dual-Prompt Agents** (auto-switch between Claude and GPT prompts):
 

docs/guide/orchestration.md

@@ -36,7 +36,7 @@ flowchart TB
     subgraph Planning["Planning Layer (Human + Prometheus)"]
         User[(" User")]
         Prometheus[" Prometheus<br/>(Planner)<br/>claude-opus-4-7 / gpt-5.5 / glm-5"]
-        Metis[" Metis<br/>(Consultant)<br/>claude-opus-4-7 / gpt-5.5 / glm-5"]
+        Metis[" Metis<br/>(Consultant)<br/>claude-sonnet-4-6 / claude-opus-4-7 / gpt-5.5 / glm-5"]
         Momus[" Momus<br/>(Reviewer)<br/>gpt-5.5 / claude-opus-4-7 / gemini-3.1-pro / glm-5"]
     end