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/features/AGENTS.md

@@ -2,18 +2,20 @@
 
 ## OVERVIEW
 
-Core feature modules + Claude Code compatibility layer. Orchestrates background agents, skill MCPs, builtin skills/commands, and 16 feature modules.
+20 feature modules: background agents, skill MCPs, builtin skills/commands, Claude Code compatibility layer.
+
+**Feature Types**: Task orchestration, Skill definitions, Command templates, Claude Code loaders, Supporting utilities
 
 ## STRUCTURE
 
 ```
 features/
-├── background-agent/           # Task lifecycle (1377 lines)
+├── background-agent/           # Task lifecycle (1418 lines)
 │   ├── manager.ts              # Launch → poll → complete
 │   └── concurrency.ts          # Per-provider limits
 ├── builtin-skills/             # Core skills (1729 lines)
-│   └── skills.ts               # agent-browser, dev-browser, frontend-ui-ux, git-master, typescript-programmer
-├── builtin-commands/           # ralph-loop, refactor, ulw-loop, init-deep, start-work, cancel-ralph
+│   └── skills.ts               # playwright, dev-browser, frontend-ui-ux, git-master, typescript-programmer
+├── builtin-commands/           # ralph-loop, refactor, ulw-loop, init-deep, start-work, cancel-ralph, stop-continuation
 ├── claude-code-agent-loader/   # ~/.claude/agents/*.md
 ├── claude-code-command-loader/ # ~/.claude/commands/*.md
 ├── claude-code-mcp-loader/     # .mcp.json with ${VAR} expansion
@@ -24,9 +26,11 @@ features/
 ├── boulder-state/              # Todo state persistence
 ├── hook-message-injector/      # Message injection
 ├── task-toast-manager/         # Background task notifications
-├── skill-mcp-manager/          # MCP client lifecycle (520 lines)
+├── skill-mcp-manager/          # MCP client lifecycle (617 lines)
 ├── tmux-subagent/              # Tmux session management
-└── ... (16 modules total)
+├── mcp-oauth/                  # MCP OAuth handling
+├── sisyphus-swarm/             # Swarm coordination
+└── sisyphus-tasks/             # Task tracking
 ```
 
 ## LOADER PRIORITY