fix(sftp): swap inbound/outbound paths — FromHPE is inbound, ToHPE is outbound

The dzinesco SP9 seed had `paths.inbound` and `paths.outbound` mapped to
the wrong Gainwell MFT directories:

  - paths.outbound  was  FromHPE/   (HPE sends files FROM here TO us — inbound)
  - paths.inbound   was  ToHPE/     (we send files TO here — outbound)

So `/api/clearhouse/submit` was writing 837P claims to FromHPE (where
HPE puts acks/835s) and the SP16 scheduler was polling ToHPE (where our
claims go). 999 / TA1 / 835 files in the real FromHPE inbox were
unreachable.

Semantics per operator (2026-06-24):
  - FromHPE = HPE/Gainwell → us  = 999, TA1, 835  (inbound)
  - ToHPE   = us → HPE/Gainwell = 837P claims    (outbound)

**Runtime code (the actual fix):**
  - backend/src/cyclone/store.py            — SP9 seed paths flipped
  - backend/src/cyclone/edi/filenames.py    — docstring corrected

**Test fixtures + assertions (would otherwise fail on the new seed):**
  - backend/tests/test_clearhouse_api.py
  - backend/tests/test_providers_seed.py
  - backend/tests/test_sftp_stub.py        — incl. inbound dir paths
  - backend/tests/test_sftp_paramiko.py
  - backend/tests/test_store_update_clearhouse.py
  - backend/tests/test_api_clearhouse_patch.py
  - backend/tests/test_scheduler.py
  - backend/tests/test_api_scheduler.py

**Docs (text-only — keeps the codebase self-consistent):**
  - README.md
  - docs/reference/co-medicaid.md
  - docs/superpowers/specs/2026-06-20-cyclone-multi-payer-npi-sftp-design.md

**Operator action required after merge:** the existing clearhouse row in
`~/.local/share/cyclone/cyclone.db` was seeded with the old wrong
paths. Easiest recovery:
  1. `rm ~/.local/share/cyclone/cyclone.db` and let `ensure_clearhouse_seeded` re-run on next boot, OR
  2. PATCH /api/clearhouse with the new `paths` block (the SP25
     reconfigure hook picks it up live, including by the running scheduler).

**Verification:**
  - 82 tests in the affected files pass (test_clearhouse_api, test_providers_seed,
    test_sftp_stub, test_sftp_paramiko, test_store_update_clearhouse,
    test_api_clearhouse_patch, test_scheduler, test_api_scheduler, test_filenames).
  - Full backend suite: 1029 pass + 36 pre-existing order-dependent flakes
    unrelated to this change (verified by running the same tests in isolation).

backend/tests/test_api_scheduler.py

@@ -34,13 +34,13 @@ def _stub_scheduler_env(tmp_path, monkeypatch):
     db._reset_for_tests()
 
     staging = tmp_path / "staging"
-    inbound = staging / "ToHPE"
+    inbound = staging / "FromHPE"
     inbound.mkdir(parents=True)
     sftp_block = SftpBlock(
         host="mft.example.com",
         port=22,
         username="test",
-        paths={"outbound": "/FromHPE", "inbound": "/ToHPE"},
+        paths={"outbound": "/ToHPE", "inbound": "/FromHPE"},
         stub=True,
         staging_dir=str(staging),
         poll_seconds=60,
@@ -54,7 +54,7 @@ def _stub_scheduler_env(tmp_path, monkeypatch):
 
 
 def _drop_file(staging: Path, name: str, body: bytes) -> Path:
-    p = staging / "ToHPE" / name
+    p = staging / "FromHPE" / name
     p.write_bytes(body)
     return p