docs: archive the improvement log/scan and the June superpowers plans

Moved to docs/archive/ (kept for their history, not deleted), each with a
one-line header saying it is historical and what supersedes it:

- IMPROVEMENT_LOG.md: three automated-loop PRs from April-May 2026, on
  the earlier quantumclaw PR numbering, which now collides with this
  repo's #12-#15. Superseded by CHANGELOG.md and git log.
- IMPROVEMENT_SCAN.md: one scan's notes (2026-05-04) of changes merged
  long ago. Superseded by CHANGELOG.md and git log.
- docs/superpowers/plans/*.md -> docs/archive/plans/: agent pre-work
  plans for d6c4d4f (2026-06-30), already marked implemented. The MPI plan
  promised collective MPI-IO, which is not what shipped (MpiVol is
  root-read + broadcast); its header says so and points at ROADMAP.md,
  where collective I/O is an open item.

Nothing links to the old paths (research/*.md mention IMPROVEMENT_LOG.md
and ROADMAP.md in prose only).

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

docs/archive/IMPROVEMENT_SCAN.md

@@ -0,0 +1,24 @@
+> **Historical (archived 2026-09-28):** one automated scan's notes (2026-05-04), describing changes long since merged. Superseded by [`CHANGELOG.md`](../../CHANGELOG.md) and `git log`.
+
+# Improvement Scan -- clawhdf5
+
+**Date:** 2026-05-04
+**Loop:** research-update-quantum
+**Branch:** research/scan-20260504-113439
+
+## Changes Made
+
+### 1. `crates/clawhdf5-agent/src/lib.rs` -- Eliminate WAL unwrap() via is_none_or + if let
+- Replaced two if self.wal.is_some() { ... self.wal.as_ref().unwrap()... } patterns
+- New: self.wal.as_ref().is_none_or(|w| ...) + if let Some(ref mut w) = self.wal
+- Eliminates 4 production unwrap() calls -- cannot panic now
+
+### 2. `crates/clawhdf5-agent/src/agents_md.rs` -- to_string() -> to_owned() on literals (3 changes)
+
+### 3. `crates/clawhdf5-agent/src/knowledge.rs` -- to_string() -> to_owned() on &str params (3 changes)
+
+### 4. `crates/clawhdf5-agent/src/query_expand.rs` -- to_string() -> to_owned() on literals (2 changes)
+
+## Gates
+- cargo clippy --workspace -- -D warnings: PASSED
+- cargo test --workspace: PASSED