feat(agents): add Hephaestus - autonomous deep worker agent (#1287)

* refactor(keyword-detector): split constants into domain-specific modules

* feat(shared): add requiresAnyModel and isAnyFallbackModelAvailable

* feat(config): add hephaestus to agent schemas

* feat(agents): add Hephaestus autonomous deep worker

* feat(cli): update model-fallback for hephaestus support

* feat(plugin): add hephaestus to config handler with ordering

* test(delegate-task): update tests for hephaestus agent

* docs: update AGENTS.md files for hephaestus

* docs: add hephaestus to READMEs

* chore: regenerate config schema

* fix(delegate-task): bypass requiresModel check when user provides explicit config

* docs(hephaestus): add 4-part context structure for explore/librarian prompts

* docs: fix review comments from cubic (non-breaking changes)

- Move Hephaestus from Primary Agents to Subagents (uses own fallback chain)
- Fix Hephaestus fallback chain documentation (claude-opus-4-5 → gemini-3-pro)
- Add settings.local.json to claude-code-hooks config sources
- Fix delegate_task parameters in ultrawork prompt (agent→subagent_type, background→run_in_background, add load_skills)
- Update line counts in AGENTS.md (index.ts: 788, manager.ts: 1440)

* docs: fix additional documentation inconsistencies from oracle review

- Fix delegate_task parameters in Background Agents example (docs/features.md)
- Fix Hephaestus fallback chain in root AGENTS.md to match model-requirements.ts

* docs: clarify Hephaestus has no fallback (requires gpt-5.2-codex only)

Hephaestus uses requiresModel constraint - it only activates when gpt-5.2-codex
is available. The fallback chain in code is unreachable, so documentation
should not mention fallbacks.

* fix(hephaestus): remove unreachable fallback chain entries

Hephaestus has requiresModel: gpt-5.2-codex which means the agent only
activates when that specific model is available. The fallback entries
(claude-opus-4-5, gemini-3-pro) were unreachable and misleading.

---------

Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>

src/agents/AGENTS.md

@@ -1,19 +1,27 @@
 # AGENTS KNOWLEDGE BASE
 
 ## OVERVIEW
-10 AI agents for multi-model orchestration. Sisyphus (primary), Atlas (orchestrator), oracle, librarian, explore, multimodal-looker, Prometheus, Metis, Momus, Sisyphus-Junior.
+
+11 AI agents for multi-model orchestration. Each agent has factory function + metadata + fallback chains.
+
+**Primary Agents** (respect UI model selection):
+- Sisyphus, Atlas, Prometheus
+
+**Subagents** (use own fallback chains):
+- Hephaestus, Oracle, Librarian, Explore, Multimodal-Looker, Metis, Momus, Sisyphus-Junior
 
 ## STRUCTURE
 ```
 agents/
 ├── atlas.ts                    # Master Orchestrator (holds todo list)
 ├── sisyphus.ts                 # Main prompt (SF Bay Area engineer identity)
+├── hephaestus.ts               # Autonomous Deep Worker (GPT 5.2 Codex, "The Legitimate Craftsman")
 ├── sisyphus-junior.ts          # Delegated task executor (category-spawned)
 ├── oracle.ts                   # Strategic advisor (GPT-5.2)
 ├── librarian.ts                # Multi-repo research (GitHub CLI, Context7)
-├── explore.ts                  # Fast contextual grep (Grok Code)
+├── explore.ts                  # Fast contextual grep (Claude Haiku)
 ├── multimodal-looker.ts        # Media analyzer (Gemini 3 Flash)
-├── prometheus-prompt.ts        # Planning (Interview/Consultant mode, 1196 lines)
+├── prometheus-prompt.ts        # Planning (Interview/Consultant mode, 1283 lines)
 ├── metis.ts                    # Pre-planning analysis (Gap detection)
 ├── momus.ts                    # Plan reviewer (Ruthless fault-finding)
 ├── dynamic-agent-prompt-builder.ts  # Dynamic prompt generation
@@ -26,6 +34,7 @@ agents/
 | Agent | Model | Temp | Purpose |
 |-------|-------|------|---------|
 | Sisyphus | anthropic/claude-opus-4-5 | 0.1 | Primary orchestrator (fallback: kimi-k2.5 → glm-4.7 → gpt-5.2-codex → gemini-3-pro) |
+| Hephaestus | openai/gpt-5.2-codex | 0.1 | Autonomous deep worker, "The Legitimate Craftsman" (requires gpt-5.2-codex, no fallback) |
 | Atlas | anthropic/claude-sonnet-4-5 | 0.1 | Master orchestrator (fallback: kimi-k2.5 → gpt-5.2) |
 | oracle | openai/gpt-5.2 | 0.1 | Consultation, debugging |
 | librarian | zai-coding-plan/glm-4.7 | 0.1 | Docs, GitHub search (fallback: glm-4.7-free) |