Give every memory a holder, an origin, a time and a scenario

An EvidenceAtom could say what was remembered and nothing else: not whose memory it
is, not where it came from, not when it was true, not in what situation it may be
used. The baseline measured the cost of that: the same ranker scores recall@10 0.412
over the whole corpus and 0.866 inside one holder's memory, so the missing holder
column is worth more than any ranking change in the ablation.

- schemas.py: MemoryOrigin, TimePrecision, Visibility; EvidenceAtom gains holder_id,
  origin, scenario, event_time / event_time_end / event_time_precision /
  event_time_source, valid_from / valid_to, supersedes, visibility, retention_until.
  `time` is renamed `ingested_at` — ingestion time gets one name, not two.
  A validator refuses valid_to before valid_from, event_time_end before event_time,
  and an atom that supersedes itself.
- migrations.py: schema v2 with PRAGMA user_version. A first-version database is
  upgraded in place (ALTER + RENAME COLUMN), rows intact, and a database newer than
  this build refuses to open instead of being silently downgraded.
- v_atoms_current hides memories that are closed, lapsed or not yet begun; unknown
  bounds read as visible. Time travel is db.atoms_as_of(moment, holder) because a
  SQLite view cannot take a parameter.
- evaluation_schemas.py: the proof and benchmark report shapes move out of schemas.py
  to keep it under the file-size limit; importers follow.
- backend/tests/test_memory_schema.py: 8 tests, including the v1 -> v2 upgrade and the
  validity timeline.

Verification of record: pytest backend/tests bench/tests -q -> 70 passed; ruff check on
every touched file -> all checks passed; mypy (fresh cache) on db.py, migrations.py,
schemas.py, evaluation_schemas.py and backend/tests -> no issues. evals.py carries 40
pre-existing mypy errors at HEAD and 40 after this change (measured on both copies);
its pyright findings are the same debt, and p0-6 rewrites that file. `peft` and
`pyarrow.parquet` "could not be resolved" is the documented pyright artifact: pi-lens
runs it with 0 config files, and both import at runtime.

backend/src/ely_eye/api.py

@@ -24,6 +24,15 @@ from .config import Settings, get_settings
 from .db import Database
 from .embeddings import EmbeddingService
 from .evals import HashHopEvaluator, PRDProofSuite
+from .evaluation_schemas import (
+    BenchmarkPredictionReport,
+    BenchmarkRegistryReport,
+    BenchmarkSampleReport,
+    BenchmarkSourceReport,
+    HashHopProof,
+    ProofCheck,
+    ProofSuiteReport,
+)
 from .evidence_graph import EvidenceGraphService
 from .ingestion import IngestionService
 from .profiles import runtime_profile_report
@@ -33,16 +42,9 @@ from .schemas import (
     AdapterManifest,
     AdapterStatus,
     AnswerResponse,
-    BenchmarkRegistryReport,
-    BenchmarkPredictionReport,
-    BenchmarkSampleReport,
-    BenchmarkSourceReport,
     CartridgeAssetReport,
-    HashHopProof,
     MemoryStatus,
     PathIngestRequest,
-    ProofCheck,
-    ProofSuiteReport,
     RuntimeProfile,
     RuntimeProfileReport,
     SystemStatus,