chore: stop shipping working material in the repository

[sshaplygin]

CLAUDE.md, codemaps/, .reports/, .vscode/ and a debug-probe test in
the metrics module were tracked, so every clone carried notes describing how
the project was built rather than how the library works. CLAUDE.md alone was
68K of stage history, and it had drifted -- several of its claims were
corrected only after an audit, and one had been wrong since the version it
described.

They are untracked rather than deleted: the files stay on disk as working
notes and as material for a retrospective write-up. Documentation a reader or
a tool should rely on lives in docs/.

lfu/simplelfu/lfu_test.go cited "CLAUDE.md rule 5" for the no-panic rule.
With the file gone from the repository that reference points at nothing, so
the comment states the rule instead of citing it.

Verification

make all                                    -> Release checks passed (10 modules)
git status --porcelain | wc -l              -> 0
git diff main...HEAD -- '**/go.mod' go.mod  -> 0 lines
                                               9 files changed, 12 insertions(+), 1710 deletions(-)

A fresh clone of this branch contains none of the removed paths, and the
metrics module still builds and passes its tests without the debug probe:
ok github.com/sshaplygin/as-cache/metrics 0.549s.

Follow-up, not in this change

The load-bearing invariants that lived in the removed file (the zero-value
rule, the switchLocked ordering rule, the three roles during a gradual
migration window, the bandit running under the write lock, why TTLCache is
not built on expirable) now exist only outside the repository. Folding them
into docs/ is the next documentation change.