refactor: major codebase cleanup - BDD comments, file splitting, bug fixes (#1350)

* style(tests): normalize BDD comments from '// #given' to '// given'

- Replace 4,668 Python-style BDD comments across 107 test files
- Patterns changed: // #given -> // given, // #when -> // when, // #then -> // then
- Also handles no-space variants: //#given -> // given

* fix(rules-injector): prefer output.metadata.filePath over output.title

- Extract file path resolution to dedicated output-path.ts module
- Prefer metadata.filePath which contains actual file path
- Fall back to output.title only when metadata unavailable
- Fixes issue where rules weren't injected when tool output title was a label

* feat(slashcommand): add optional user_message parameter

- Add user_message optional parameter for command arguments
- Model can now call: command='publish' user_message='patch'
- Improves error messages with clearer format guidance
- Helps LLMs understand correct parameter usage

* feat(hooks): restore compaction-context-injector hook

- Restore hook deleted in cbbc7bd0 for session compaction context
- Injects 7 mandatory sections: User Requests, Final Goal, Work Completed,
  Remaining Tasks, Active Working Context, MUST NOT Do, Agent Verification State
- Re-register in hooks/index.ts and main plugin entry

* refactor(background-agent): split manager.ts into focused modules

- Extract constants.ts for TTL values and internal types (52 lines)
- Extract state.ts for TaskStateManager class (204 lines)
- Extract spawner.ts for task creation logic (244 lines)
- Extract result-handler.ts for completion handling (265 lines)
- Reduce manager.ts from 1377 to 755 lines (45% reduction)
- Maintain backward compatible exports

* refactor(agents): split prometheus-prompt.ts into subdirectory

- Move 1196-line prometheus-prompt.ts to prometheus/ subdirectory
- Organize prompt sections into separate files for maintainability
- Update agents/index.ts exports

* refactor(delegate-task): split tools.ts into focused modules

- Extract categories.ts for category definitions and routing
- Extract executor.ts for task execution logic
- Extract helpers.ts for utility functions
- Extract prompt-builder.ts for prompt construction
- Reduce tools.ts complexity with cleaner separation of concerns

* refactor(builtin-skills): split skills.ts into individual skill files

- Move each skill to dedicated file in skills/ subdirectory
- Create barrel export for backward compatibility
- Improve maintainability with focused skill modules

* chore: update import paths and lockfile

- Update prometheus import path after refactor
- Update bun.lock

* fix(tests): complete BDD comment normalization

- Fix remaining #when/#then patterns missed by initial sed
- Affected: state.test.ts, events.test.ts

---------

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

src/tools/delegate-task/categories.ts

@@ -0,0 +1,70 @@
+import type { CategoryConfig, CategoriesConfig } from "../../config/schema"
+import { DEFAULT_CATEGORIES, CATEGORY_PROMPT_APPENDS } from "./constants"
+import { resolveModel } from "../../shared"
+import { isModelAvailable } from "../../shared/model-availability"
+import { CATEGORY_MODEL_REQUIREMENTS } from "../../shared/model-requirements"
+import { log } from "../../shared"
+
+export interface ResolveCategoryConfigOptions {
+  userCategories?: CategoriesConfig
+  inheritedModel?: string
+  systemDefaultModel?: string
+  availableModels?: Set<string>
+}
+
+export interface ResolveCategoryConfigResult {
+  config: CategoryConfig
+  promptAppend: string
+  model: string | undefined
+}
+
+/**
+ * Resolve the configuration for a given category name.
+ * Merges default and user configurations, handles model resolution.
+ */
+export function resolveCategoryConfig(
+  categoryName: string,
+  options: ResolveCategoryConfigOptions
+): ResolveCategoryConfigResult | null {
+  const { userCategories, inheritedModel, systemDefaultModel, availableModels } = options
+
+  // Check if category requires a specific model
+  const categoryReq = CATEGORY_MODEL_REQUIREMENTS[categoryName]
+  if (categoryReq?.requiresModel && availableModels) {
+    if (!isModelAvailable(categoryReq.requiresModel, availableModels)) {
+      log(`[resolveCategoryConfig] Category ${categoryName} requires ${categoryReq.requiresModel} but not available`)
+      return null
+    }
+  }
+
+  const defaultConfig = DEFAULT_CATEGORIES[categoryName]
+  const userConfig = userCategories?.[categoryName]
+  const defaultPromptAppend = CATEGORY_PROMPT_APPENDS[categoryName] ?? ""
+
+  if (!defaultConfig && !userConfig) {
+    return null
+  }
+
+  // Model priority for categories: user override > category default > system default
+  // Categories have explicit models - no inheritance from parent session
+  const model = resolveModel({
+    userModel: userConfig?.model,
+    inheritedModel: defaultConfig?.model, // Category's built-in model takes precedence over system default
+    systemDefault: systemDefaultModel,
+  })
+  const config: CategoryConfig = {
+    ...defaultConfig,
+    ...userConfig,
+    model,
+    variant: userConfig?.variant ?? defaultConfig?.variant,
+  }
+
+  let promptAppend = defaultPromptAppend
+  if (userConfig?.prompt_append) {
+    promptAppend = defaultPromptAppend
+      ? defaultPromptAppend + "\n\n" + userConfig.prompt_append
+      : userConfig.prompt_append
+  }
+
+  return { config, promptAppend, model }
+}