The regex provider is documented under its retired name regexp #678

Epic: #454
Plan: docs/plans/regex-provider-naming.md

The regexp provider was renamed to regex in code — directory, package, and Starlark-facing name. The design
record never followed.

• pkg/op/provider/regex/action_names.gen.go:16 announces regex.find
• docs/architecture/3.5-provider-catalog.md:48 still says regexp / regexp.*, in a table that calls itself
  "the index of record for every provider"
• the design doc and its status companion are still filed as 3.5.15-regexp-provider.md
• the status doc's test matrix cites test_regexp.star and test_imm_regexp.star — neither exists; the
  fixture is cmd/devlore-test/devloretest/data/test_regex.star

23 regexp references across 6 architecture files. 7-registry-knowledge.md's 8 hits need per-line triage:
Go stdlib *regexp.Regexp in code samples is correct and stays.

Plan documents describing pre-rename work keep their prose — that was the correct name when written. Only stale
code paths are corrected.