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/hooks/prometheus-md-only/agent-resolution.ts

@@ -0,0 +1,52 @@
+import { existsSync, readdirSync } from "node:fs"
+import { join } from "node:path"
+import { findNearestMessageWithFields, findFirstMessageWithAgent, MESSAGE_STORAGE } from "../../features/hook-message-injector"
+import { getSessionAgent } from "../../features/claude-code-session-state"
+import { readBoulderState } from "../../features/boulder-state"
+
+function getMessageDir(sessionID: string): string | null {
+  if (!existsSync(MESSAGE_STORAGE)) return null
+
+  const directPath = join(MESSAGE_STORAGE, sessionID)
+  if (existsSync(directPath)) return directPath
+
+  for (const dir of readdirSync(MESSAGE_STORAGE)) {
+    const sessionPath = join(MESSAGE_STORAGE, dir, sessionID)
+    if (existsSync(sessionPath)) return sessionPath
+  }
+
+  return null
+}
+
+function getAgentFromMessageFiles(sessionID: string): string | undefined {
+  const messageDir = getMessageDir(sessionID)
+  if (!messageDir) return undefined
+  return findFirstMessageWithAgent(messageDir) ?? findNearestMessageWithFields(messageDir)?.agent
+}
+
+/**
+ * Get the effective agent for the session.
+ * Priority order:
+ * 1. In-memory session agent (most recent, set by /start-work)
+ * 2. Boulder state agent (persisted across restarts, fixes #927)
+ * 3. Message files (fallback for sessions without boulder state)
+ *
+ * This fixes issue #927 where after interruption:
+ * - In-memory map is cleared (process restart)
+ * - Message files return "prometheus" (oldest message from /plan)
+ * - But boulder.json has agent: "atlas" (set by /start-work)
+ */
+export function getAgentFromSession(sessionID: string, directory: string): string | undefined {
+  // Check in-memory first (current session)
+  const memoryAgent = getSessionAgent(sessionID)
+  if (memoryAgent) return memoryAgent
+
+  // Check boulder state (persisted across restarts) - fixes #927
+  const boulderState = readBoulderState(directory)
+  if (boulderState?.session_ids.includes(sessionID) && boulderState.agent) {
+    return boulderState.agent
+  }
+
+  // Fallback to message files
+  return getAgentFromMessageFiles(sessionID)
+}