safe-bash: add `pr` (paginate/columnate for printing)

[kamilio]

Missing: pr. No pagination/header/column formatting of text.

Behavior: GNU pr [-COLUMNS] [-h HEADER] [-l LINES] [-w WIDTH] [-t] [-n] [-m] [-s SEP]. Pure text transform; bound page/column counts and input.

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 on remote main: 2eb8957. Five atomic commits implement bounded GNU pr, repair shared DeviceFS acquisition and enrolled-output cancellation, and correct two validated integration fixtures. Required pagination/header/column/number/merge/separator behavior is covered by native byte/status comparisons and actual saved VFS scripts; limits and qualified differences are documented in packages/safe-bash/docs/PR.md. Full maintained npm test, final repository lint, normal build, strict types, package lint and the exact committed-archive gate pass. All 22 fresh packed profiles pass, including pr factory/subpath identity and both shared-fix cancellation canaries; all 55 input hashes and built/packed closures remain unchanged. Browser-platform bundles ran in Node, not an actual browser. Release workflows are being monitored separately; this closure records verified remote-main delivery, not yet publication.

[kamilio]

Follow-up validation found a concrete readable-device gap: GNU 8.30 pr -t /dev/null exits 0 with empty stdout/stderr, but current virtual pr exits 1 with "Operation not supported" because its reader accepts only regular-file stats. The same gap was detected in the in-progress tsort implementation. Native and actual-Shell evidence is preserved in out/issue681/null-input-red-v1.json. Reopening while a focused VFS-readable-character-device fix and regressions are implemented; this does not call the preceding qualified test/release results universal GNU parity.

[kamilio]

The separately validated readable-device follow-up is now verified on remote main at 44a14eb (fix commit 82b8af9). Virtual /dev/null, symlinks, and bounded provider-backed character streams now use the existing reader; no host fallback or pathname special case. TDD recorded 17 device failures before the fix; 134 author pr cases and 141 independent/device cases pass. Full npm test, lint, final normal build, maintained types, committed archive, package lint and 22 fresh packed profiles pass. Packed pr device statuses are checked individually. Release publication is being monitored separately; this closure confirms remote-main delivery, not publication.

[kamilio]

Reopening for a newly validated direct-public-factory cancellation gap found during factor review. If a supplied stdin iterator-factory/next getter or stderr capability/write getter synchronously aborts, the acquired method can still run afterward. Sixteen pr regressions reproduce this with false, 0, empty-string and null reasons. The delivered null-device fix remains valid; this is a separate callback-admission boundary, not a release/CI failure. The bounded follow-up is being fixed and independently retested before another verified-main closure.

[kamilio]

The follow-up is now verified on remote main at 73cdc99 (separate fix c83a414). Iterator factory/next, stderr capability/write, and VFS stat/capabilitiesFor/readStream/readFile accessors are captured once with cancellation rechecked before invoking their methods, preserving the receiver. All 64 unchanged independent pr/tsort regressions and 232 existing author cases pass, including admitted readStream body-abort cleanup controls. Full npm test, lint, final build, types, exact archive, package lint and 22 fresh packed profiles pass. Eight direct-factory packed canaries exercise the fix alongside earlier Shell/device/cleanup checks. This closes the validated follow-up after remote delivery; actual publication is monitored separately.