safe-bash: add `csplit` (context/pattern split)

[kamilio]

Missing: csplit. split (size/line chunks) exists but not pattern/line-number context splitting.

Behavior: GNU csplit [-f PREFIX] [-b SUFFIX] [-k] [-z] FILE PATTERN… with /regex/, %regex%, {N}/{*} repeats, line numbers, +/- offsets. Route regexes through the bounded regex executor; cap output-file count.

From the safe-bash command gap analysis (2026-09-08). Sandbox constraints apply: bounded input/CPU/memory, VFS-only paths, cooperative cancellation, no host process/network beyond the existing curl authorizer.

[kamilio]

Verified delivered on remote main: b270fe0 (feat(safe-bash): add bounded GNU csplit). Includes bounded shared BRE search, VFS output ownership/cleanup, default registration and root/scoped/browser exports. GNU 8.30 source and native byte/status/filesystem-effect comparisons informed implementation; limits and qualified compatibility boundaries are documented in packages/safe-bash/docs/CSPLIT.md. Final maintained full npm test, repository lint, normal workspace build, types and package lint pass; committed-archive consumer and 22 fresh packed profiles pass. Browser-platform bundles were executed in Node, not an actual browser. Remote release runs are being monitored separately; this closure records verified main delivery, not publication.

[kamilio]

Publication follow-up: Release 34439408322 successfully published poe-code@15.0.7 on September 10, 2026 at 05:24:37 UTC. Independent npm checks verified latest and exact-version gitHead b270fe0. Scoped safe packages 0.1.535, Toolcraft packages 0.0.218 and Pages also succeeded. This verifies publication separately from remote-main delivery; the documented bounded compatibility profile is unchanged.