safe-bash: add `tsort` (topological sort)

[kamilio]

Missing: tsort. No topological ordering of dependency pairs.

Behavior: GNU tsort [FILE] reads whitespace-separated node pairs, emits a topological order, and reports cycles on stderr with a non-zero exit. Bound node/edge counts; detect cycles deterministically.

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]

Implemented and verified on remote main at 44a14eb. Read the full pinned GNU 8.30 tsort source; exact finite native stdout/stderr/status comparisons cover ordering, FIFO successors, cycles, options and raw-byte/NUL cases. Adds bounded graph/input/work/storage/output, cooperative cancellation, VFS devices, factories/default preset and root/scoped Node/browser subpaths. Author 98 and independent 93 cases pass. Full npm test, lint, final normal build, types, exact committed archive, package lint and 22 fresh packed profiles pass; saved VFS scripts and terminal output were inspected. Limits and qualified differences are documented in packages/safe-bash/docs/TSORT.md; no universal GNU parity claim. Release publication is monitored separately while work continues on #682.

[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 tsort regressions reproduce this with false, 0, empty-string and null reasons. Native ordering/device behavior remains validated; this is a separate callback-admission boundary, not a release/CI failure. A bounded follow-up is being fixed and independently retested before another verified-main closure.

[kamilio]

The direct-factory cancellation follow-up is verified on remote main at 73cdc99 (separate fix c83a414). Cancellation is rechecked after iterator, stderr and VFS provider method accessors, before invoking acquired methods; original receivers and already-admitted source cleanup are preserved. All 64 unchanged independent getter regressions and 232 existing pr/tsort author cases pass. Full npm test, lint, final build, types, exact archive, package lint and 22 fresh packed profiles pass, including public direct-factory canaries and prior native-ordering/device checks. Release publication is monitored separately; no universal host-JavaScript preemption claim.