fix: restore CLAUDE.md importing AGENTS.md

[lesnik512]

Summary

Restores a CLAUDE.md that imports AGENTS.md. Without it, Claude Code loads no project
instructions for this repo.

The rename to AGENTS.md was made on the belief that Claude Code discovers AGENTS.md natively.
It does not. The documentation is explicit:

Claude Code reads CLAUDE.md, not AGENTS.md.

The test that appeared to show otherwise was invalid: it ran with file tools available, so the model
simply read AGENTS.md off disk rather than receiving it as loaded context. Re-run with file tools
denied, a directory containing only AGENTS.md reports the instructions are not in context,
while a real CLAUDE.md control reports them correctly.

Changes

Adds a one-line CLAUDE.md:

@AGENTS.md

AGENTS.md remains the single home of the content — this is an import, not a copy, so the two
cannot drift. Claude Code expands it at session start.

Why an import rather than a symlink

Both work — each was verified with file tools denied. The import is preferred because a symlink
requires Administrator privileges or Developer Mode on Windows; without them the checkout gets a
plain text file containing the target path, which loads as garbage. The import is also the form the
documentation recommends, and it leaves room to append Claude-specific instructions below it later.

Part of modern-python/.github#51.

[github-actions]

Benchmark gate

✅ gate passed

scenario	msg/s	delete/msg	WALrec/msg	WALB/msg	fpi	upd	del	dead_tup
consumer/w1/b10	820	1.000	6.83	910	242	5000	5000	10000
consumer/w1/b100	1205	1.000	6.89	917	243	5000	5000	10000
consumer/w2/b10	1407	1.000	6.78	952	242	5000	5000	10000
consumer/w2/b100	1297	1.000	6.79	994	263	5000	5000	10000
consumer/w4/b10	1145	1.000	6.67	921	243	5000	5000	10000
consumer/w4/b100	1050	1.000	6.85	1029	243	5000	5000	10000
consumer/w1/b100/tfbs100	5320	0.010	6.07	1116	243	5000	5000	10000
producer/w1/b100	4197	0.000	3.04	584	0	0	0	0

Gated (fails the build): delete_calls + tuple counters (upd/del/ins) + the producer's insert_calls, exact; select_calls within +2; wal_records within a 10% band. msg/s, WAL bytes and total calls are informational (timing/FPI noise).