fix(scheduler): read inbound bytes from the cached local_path, not read_file(f.name)

In real (paramiko) mode, `_download_and_parse` called
`client.read_file(f.name)` with a bare filename. paramiko's
`sftp.open(f.name)` opens at the SFTP root, not at `paths.inbound`
(FromHPE) — so the scheduler would fail to download any file in real
mode even with the path swap from the previous commit.

But this round-trip is also unnecessary: `_list_inbound_paramiko`
already downloads each entry into the local cache (cache_path) and
returns it as `InboundFile.local_path` as part of the listing pass.
Reading from disk is faster than re-fetching and avoids the path bug.

Stub mode was already reading from `f.local_path`. Now both modes do,
which is the simpler invariant.

Verified: 36 tests pass (test_scheduler, test_api_scheduler, test_sftp_stub,
test_sftp_paramiko).

backend/src/cyclone/scheduler.py

@@ -650,20 +650,21 @@ class Scheduler:
     def _download_and_parse(
         self, f: InboundFile, file_type: str,
     ) -> tuple[Path, str, int]:
-        """Download from MFT, run the right handler. Returns (path, parser, count).
+        """Run the right handler on one inbound file. Returns (path, parser, count).
 
-        Stub mode: ``f.local_path`` already points at the staged file
-        (set by ``SftpClient._list_inbound_stub``). Real mode: the
-        remote name is ``f.name`` and we round-trip through paramiko.
+        Both stub and real modes read from ``f.local_path`` — the
+        inbound file is already on disk:
+          * Stub mode: ``_list_inbound_stub`` points ``local_path`` at
+            the operator-dropped staging file.
+          * Real mode: ``_list_inbound_paramiko`` downloads each
+            ``listdir_attr`` entry into the local cache as part of the
+            listing pass. Re-reading from the MFT would require
+            ``SftpClient.read_file`` with a full remote path, which the
+            scheduler was passing just ``f.name`` for (i.e. a bare
+            filename at the SFTP root, not the inbound dir). Use the
+            cached bytes instead.
         """
-        if self._sftp_block.stub:
-            # In stub mode the InboundFile already has a local_path;
-            # reading the staged bytes directly avoids the stub's
-            # remote-path semantics (which expect a full inbound path).
         content = f.local_path.read_bytes()
-        else:
-            client = self._sftp_client_factory(self._sftp_block)
-            content = client.read_file(f.name)
         text = content.decode("utf-8")
         handler = HANDLERS[file_type]
         parser_used, claim_count = handler(text, f.name)