refactor: wave 1 - extract leaf modules, rename catch-all files, split index.ts hooks

- Split 25+ index.ts files into hook.ts + extracted modules
- Rename all catch-all utils.ts/helpers.ts to domain-specific names
- Split src/tools/lsp/ into ~15 focused modules
- Split src/tools/delegate-task/ into ~18 focused modules
- Separate shared types from implementation
- 155 files changed, 60+ new files created
- All typecheck clean, 61 tests pass

src/agents/builtin-agents/agent-overrides.ts

@@ -0,0 +1,61 @@
+import type { AgentConfig } from "@opencode-ai/sdk"
+import type { AgentOverrideConfig } from "../types"
+import type { CategoryConfig } from "../../config/schema"
+import { deepMerge, migrateAgentConfig } from "../../shared"
+
+/**
+ * Expands a category reference from an agent override into concrete config properties.
+ * Category properties are applied unconditionally (overwriting factory defaults),
+ * because the user's chosen category should take priority over factory base values.
+ * Direct override properties applied later via mergeAgentConfig() will supersede these.
+ */
+export function applyCategoryOverride(
+  config: AgentConfig,
+  categoryName: string,
+  mergedCategories: Record<string, CategoryConfig>
+): AgentConfig {
+  const categoryConfig = mergedCategories[categoryName]
+  if (!categoryConfig) return config
+
+  const result = { ...config } as AgentConfig & Record<string, unknown>
+  if (categoryConfig.model) result.model = categoryConfig.model
+  if (categoryConfig.variant !== undefined) result.variant = categoryConfig.variant
+  if (categoryConfig.temperature !== undefined) result.temperature = categoryConfig.temperature
+  if (categoryConfig.reasoningEffort !== undefined) result.reasoningEffort = categoryConfig.reasoningEffort
+  if (categoryConfig.textVerbosity !== undefined) result.textVerbosity = categoryConfig.textVerbosity
+  if (categoryConfig.thinking !== undefined) result.thinking = categoryConfig.thinking
+  if (categoryConfig.top_p !== undefined) result.top_p = categoryConfig.top_p
+  if (categoryConfig.maxTokens !== undefined) result.maxTokens = categoryConfig.maxTokens
+
+  return result as AgentConfig
+}
+
+export function mergeAgentConfig(base: AgentConfig, override: AgentOverrideConfig): AgentConfig {
+  const migratedOverride = migrateAgentConfig(override as Record<string, unknown>) as AgentOverrideConfig
+  const { prompt_append, ...rest } = migratedOverride
+  const merged = deepMerge(base, rest as Partial<AgentConfig>)
+
+  if (prompt_append && merged.prompt) {
+    merged.prompt = merged.prompt + "\n" + prompt_append
+  }
+
+  return merged
+}
+
+export function applyOverrides(
+  config: AgentConfig,
+  override: AgentOverrideConfig | undefined,
+  mergedCategories: Record<string, CategoryConfig>
+): AgentConfig {
+  let result = config
+  const overrideCategory = (override as Record<string, unknown> | undefined)?.category as string | undefined
+  if (overrideCategory) {
+    result = applyCategoryOverride(result, overrideCategory, mergedCategories)
+  }
+
+  if (override) {
+    result = mergeAgentConfig(result, override)
+  }
+
+  return result
+}