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

src/tools/AGENTS.md

@@ -48,20 +48,20 @@ Tools registered via [`createToolRegistry()`](file:///Users/yeongyu/local-worksp
 
 ## DELEGATION CATEGORIES (built-in 8)
 
-`task` (delegate) selects model by category; categories defined in `delegate-task/constants.ts`:
+`task` (delegate) selects model by category. Default category models live in provider-specific files under `src/tools/delegate-task/` and aggregate via `BUILTIN_CATEGORIES` in `builtin-categories.ts`. Authoritative fallback chains in [`src/shared/model-requirements.ts`](file:///Users/yeongyu/local-workspaces/omo/src/shared/model-requirements.ts) `CATEGORY_MODEL_REQUIREMENTS`.
 
-| Category | Default Model | Domain |
-|----------|---------------|--------|
-| `visual-engineering` | gemini-3.1-pro high | Frontend, UI/UX |
-| `ultrabrain` | gpt-5.5 xhigh | Hard logic / heavy reasoning |
-| `deep` | gpt-5.5 medium | Autonomous multi-step problem-solving |
-| `artistry` | gemini-3.1-pro high | Creative / unconventional approaches |
-| `quick` | gpt-5.4-mini-fast | Trivial single-file changes |
-| `unspecified-low` | claude-sonnet-4-6 | Moderate effort fallback |
-| `unspecified-high` | claude-opus-4-7 max | High effort fallback |
-| `writing` | gemini-3-flash | Documentation, prose |
+| Category | Default Model | Source File | Domain |
+|----------|---------------|-------------|--------|
+| `visual-engineering` | google/gemini-3.1-pro (variant: high) | google-categories.ts | Frontend, UI/UX |
+| `ultrabrain` | openai/gpt-5.5 (variant: xhigh) | openai-categories.ts | Hard logic / heavy reasoning |
+| `deep` | openai/gpt-5.5 (variant: medium) | openai-categories.ts | Autonomous multi-step problem-solving |
+| `artistry` | google/gemini-3.1-pro (variant: high) | google-categories.ts | Creative / unconventional approaches |
+| `quick` | openai/gpt-5.4-mini | openai-categories.ts | Trivial single-file changes |
+| `unspecified-low` | anthropic/claude-sonnet-4-6 | anthropic-categories.ts | Moderate effort fallback |
+| `unspecified-high` | anthropic/claude-opus-4-7 (variant: max) | anthropic-categories.ts | High effort fallback |
+| `writing` | kimi-for-coding/k2p5 (default) → gemini-3-flash (first fallback) | kimi-categories.ts | Documentation, prose |
 
-User-defined categories declared in `categories: { ... }` config override and add to this set.
+User-defined categories declared in `categories: { ... }` config override and extend this set.
 
 ## TOOL DIR LAYOUT