docs: document manual SFTP mode for this host (post-SP36)

- .env.example: add GAINWELL_SFTP_* mirror vars with bridge instructions
- .gitignore: exclude ingest/ + macOS AppleDouble residue
- CLAUDE.md: 'Production SFTP posture' section (env bridge, inbound drop
  zone, auth caveat, ingestion paths, daemon hot-reload caveat)
- docs/RUNBOOK.md: 'Manual SFTP mode' section (daily flow, backfill,
  parse-CLI caveat, manual→real switch procedure)

Recalibration after the auth-failed incident from 103.14.26.95 — local
SFTP uploads won't work until Gainwell whitelists this IP, so the
canonical flow is now manual file copy + cyclone pull-inbound.

.gitignore

@@ -20,6 +20,16 @@ build/
 *.swp
 *.swo
 
+# macOS extraction residue (AppleDouble / __MACOSX from unzip on macOS).
+# These are paired with every regular file in an extracted zip — never data.
+__MACOSX/
+._*
+
+# Operator drop zone (untracked working dir; contents are HCPF-delivered
+# inbound files, never source). Use `mkdir -p ingest && touch ingest/.gitkeep`
+# if you want the directory itself in the repo.
+ingest/
+
 # Local config
 .env
 .env.local