feat(uploads): guide agent using agentic search for uploaded documents (#1816)

* feat(uploads): guide agent to use grep/glob/read_file for uploaded documents

Add workflow guidance to the <uploaded_files> context block so the agent
knows to use grep and glob (added in #1784) alongside read_file when
working with uploaded documents, rather than falling back to web search.

This is the final piece of the three-PR PDF agentic search pipeline:
- PR1 (#1727): pymupdf4llm converter produces structured Markdown with headings
- PR2 (#1738): document outline injected into agent context with line numbers
- PR3 (this):  agent guided to use outline + grep + read_file workflow

* feat(uploads): add file-first priority and fallback guidance to uploaded_files context

backend/packages/harness/deerflow/agents/middlewares/uploads_middleware.py

@@ -102,7 +102,13 @@ class UploadsMiddleware(AgentMiddleware[UploadsMiddlewareState]):
             for file in historical_files:
                 self._format_file_entry(file, lines)
 
-        lines.append("You can read these files using the `read_file` tool with the paths shown above.")
+        lines.append("To work with these files:")
+        lines.append("- Read from the file first — use the outline line numbers and `read_file` to locate relevant sections.")
+        lines.append("- Use `grep` to search for keywords when you are not sure which section to look at")
+        lines.append("  (e.g. `grep(pattern='revenue', path='/mnt/user-data/uploads/')`).")
+        lines.append("- Use `glob` to find files by name pattern")
+        lines.append("  (e.g. `glob(pattern='**/*.md', path='/mnt/user-data/uploads/')`).")
+        lines.append("- Only fall back to web search if the file content is clearly insufficient to answer the question.")
         lines.append("</uploaded_files>")
 
         return "\n".join(lines)