Give the write path a CLI and an MCP face

remember / supersede / forget now reach the one Python writer from a
terminal, from MCP, and from HTTP. The server, not the caller, decides
who owns a memory.

- cli: remember, supersede, forget. --holder falls back to
  settings.default_holder until the holder registry lands. Timestamps are
  parsed once with one clear message.
- ingestion: import pymupdf as fitz. The deprecated fitz import printed a
  warning to stdout, so every CLI command's JSON answer was unparseable.
- mcp: remember, supersede_memory and forget_memory forward to the Python
  writer over HTTP (ELY_EYE_API, default http://127.0.0.1:8765). SQLite
  stays read-only to the Go side, so the write rules live in one place.
- mcp reads follow schema v2: atoms.time became ingested_at, and reads go
  through v_atoms_current, so a superseded memory stops being findable.
  holder, origin, scenario and event_time now show up in fetch_atom and
  search_atoms.
- scripts/mcp_write_smoke.sh proves the loop end to end: remember, search,
  supersede, forget, then not found.

Evidence: 92 pytest passed; go build, go vet and go test clean; mypy clean
on the 10 touched source files with a fresh cache; ruff clean except a
pre-existing B008 at cli.py:292, identical at HEAD.

backend/src/ely_eye/config.py

@@ -12,6 +12,7 @@ class Settings(BaseSettings):
     model_config = SettingsConfigDict(env_prefix="ELY_EYE_", env_file=".env", extra="ignore")
 
     home: Path = Field(default_factory=lambda: Path.cwd() / ".ely_eye")
+    default_holder: str = "local"
     model_id: str = "Qwen/Qwen3.5-9B"
     planner_model_id: str = "Qwen/Qwen3.5-0.8B"
     embedding_model_id: str = "Qwen/Qwen3-VL-Embedding-8B"