skillscript-runtime v0.26.1

Upgrade impact: none (additive). New discovery field; no behavior change.

• runtime_capabilities now reports fsExecution — the filesystem allowlist, mirroring the existing shellExecution. An author could already discover which shell binaries were permitted but had no way to learn which filesystem roots file_read/file_write may touch short of trial-and-error or asking the operator (adopter finding 35f669cb, hit independently while wiring the file_read attachment skill). fsExecution.allowlist lists the allowed absolute roots (or "(unset — default-deny)"), with a description covering the three config paths. Because the roots are reported in the runtime's filesystem namespace, this also answers the cross-namespace "what's the runtime-side path?" question — an authoring agent in a different namespace (container vs the runtime host) can read the runtime's path vocabulary directly instead of guessing its local alias.