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/tools/delegate-task/parent-context-resolver.ts

@@ -0,0 +1,38 @@
+import type { ToolContextWithMetadata } from "./types"
+import type { ParentContext } from "./executor-types"
+import { findNearestMessageWithFields, findFirstMessageWithAgent } from "../../features/hook-message-injector"
+import { getSessionAgent } from "../../features/claude-code-session-state"
+import { log, getMessageDir } from "../../shared"
+
+export function resolveParentContext(ctx: ToolContextWithMetadata): ParentContext {
+  const messageDir = getMessageDir(ctx.sessionID)
+  const prevMessage = messageDir ? findNearestMessageWithFields(messageDir) : null
+  const firstMessageAgent = messageDir ? findFirstMessageWithAgent(messageDir) : null
+  const sessionAgent = getSessionAgent(ctx.sessionID)
+  const parentAgent = ctx.agent ?? sessionAgent ?? firstMessageAgent ?? prevMessage?.agent
+
+  log("[task] parentAgent resolution", {
+    sessionID: ctx.sessionID,
+    messageDir,
+    ctxAgent: ctx.agent,
+    sessionAgent,
+    firstMessageAgent,
+    prevMessageAgent: prevMessage?.agent,
+    resolvedParentAgent: parentAgent,
+  })
+
+  const parentModel = prevMessage?.model?.providerID && prevMessage?.model?.modelID
+    ? {
+        providerID: prevMessage.model.providerID,
+        modelID: prevMessage.model.modelID,
+        ...(prevMessage.model.variant ? { variant: prevMessage.model.variant } : {}),
+      }
+    : undefined
+
+  return {
+    sessionID: ctx.sessionID,
+    messageID: ctx.messageID,
+    agent: parentAgent,
+    model: parentModel,
+  }
+}