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/path-policy.ts

@@ -0,0 +1,41 @@
+import { relative, resolve, isAbsolute } from "node:path"
+
+import { ALLOWED_EXTENSIONS } from "./constants"
+
+/**
+ * Cross-platform path validator for Prometheus file writes.
+ * Uses path.resolve/relative instead of string matching to handle:
+ * - Windows backslashes (e.g., .sisyphus\\plans\\x.md)
+ * - Mixed separators (e.g., .sisyphus\\plans/x.md)
+ * - Case-insensitive directory/extension matching
+ * - Workspace confinement (blocks paths outside root or via traversal)
+ * - Nested project paths (e.g., parent/.sisyphus/... when ctx.directory is parent)
+ */
+export function isAllowedFile(filePath: string, workspaceRoot: string): boolean {
+  // 1. Resolve to absolute path
+  const resolved = resolve(workspaceRoot, filePath)
+
+  // 2. Get relative path from workspace root
+  const rel = relative(workspaceRoot, resolved)
+
+  // 3. Reject if escapes root (starts with ".." or is absolute)
+  if (rel.startsWith("..") || isAbsolute(rel)) {
+    return false
+  }
+
+  // 4. Check if .sisyphus/ or .sisyphus\ exists anywhere in the path (case-insensitive)
+  // This handles both direct paths (.sisyphus/x.md) and nested paths (project/.sisyphus/x.md)
+  if (!/\.sisyphus[/\\]/i.test(rel)) {
+    return false
+  }
+
+  // 5. Check extension matches one of ALLOWED_EXTENSIONS (case-insensitive)
+  const hasAllowedExtension = ALLOWED_EXTENSIONS.some(
+    ext => resolved.toLowerCase().endsWith(ext.toLowerCase())
+  )
+  if (!hasAllowedExtension) {
+    return false
+  }
+
+  return true
+}