fix: correct DirSize/MD5 polling — initial_delay=0 and MD5 status v1

Live NAS investigation (test_dirsize_md5.py) revealed two bugs:

1. _poll_task() always slept 200ms before the first status call.
   DirSize and MD5 complete near-instantly on small data, so the result
   window closes before the first poll. Fix: add initial_delay parameter
   (default 0.2s for CopyMove/Delete/Compress/Extract); DirSize and MD5
   pass initial_delay=0.0 to poll immediately after start.

2. get_md5 used status version=2, but the NAS only serves the result on
   status v1 (v2 always returns 599 regardless of timing). Fix: change
   _poll_task version to 1 for SYNO.FileStation.MD5.

MD5 is one-shot: the result is consumed on the first successful status
read. Polling at 0ms ensures we catch it before it expires.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/mcp_synology_filestation/tools/filestation.py

@@ -61,13 +61,21 @@ def register_filestation(
 
     # ── internal polling helper ───────────────────────────────────────────
 
-    async def _poll_task(api: str, version: int, taskid: str) -> tuple[bool, dict[str, Any] | str]:
-        """Poll a DSM async task (CopyMove / Delete) until finished or timeout.
+    async def _poll_task(
+        api: str,
+        version: int,
+        taskid: str,
+        initial_delay: float = 0.2,
+    ) -> tuple[bool, dict[str, Any] | str]:
+        """Poll a DSM async task until finished or timeout.
 
         Args:
             api: DSM API name (e.g. "SYNO.FileStation.CopyMove").
             version: API version to use for the status call.
             taskid: Task ID returned by the corresponding start method.
+            initial_delay: Seconds to wait before the first status poll.
+                Set to 0.0 for tasks that may finish before the first poll
+                interval (e.g. DirSize on small directories, MD5 on small files).
 
         Returns:
             ``(True, status_dict)`` on success, or ``(False, "Error: …")`` on
@@ -76,13 +84,13 @@ def register_filestation(
         from mcp_synology_filestation.client import SynologyError as _SynologyError
 
         delay = 0.2
-        elapsed = 0.0
+        elapsed = initial_delay
         timeout = 60.0
 
-        while True:
-            await asyncio.sleep(delay)
-            elapsed += delay
+        if initial_delay > 0:
+            await asyncio.sleep(initial_delay)
 
+        while True:
             try:
                 status_data = await client.request(
                     api,
@@ -102,6 +110,8 @@ def register_filestation(
                     "Error: Operation timed out after 60 seconds — check NAS manually.",
                 )
 
+            await asyncio.sleep(delay)
+            elapsed += delay
             delay = min(delay * 2, 2.0)
 
     @mcp.tool()
@@ -805,7 +815,7 @@ def register_filestation(
         if not taskid:
             return "Error: DSM did not return a task ID."
 
-        ok, result = await _poll_task("SYNO.FileStation.DirSize", 1, taskid)
+        ok, result = await _poll_task("SYNO.FileStation.DirSize", 1, taskid, initial_delay=0.0)
         if not ok:
             return result  # type: ignore[return-value]
 
@@ -866,7 +876,7 @@ def register_filestation(
         if not taskid:
             return "Error: DSM did not return a task ID."
 
-        ok, result = await _poll_task("SYNO.FileStation.MD5", 2, taskid)
+        ok, result = await _poll_task("SYNO.FileStation.MD5", 1, taskid, initial_delay=0.0)
         if not ok:
             return result  # type: ignore[return-value]