Add durable fake SMS service runner

[isomorphisms]

Adds the filesystem service glue for the first Idriç SMS milestone.

This is stacked on isomorphisms/Idric-Net#6 for the compiled deterministic request parser.

• receives a trusted SMS envelope and resolves an address to a non-privileged principal
• preserves the original inbound request and per-event consent provenance
• persists one-time reminders in ordinary directories and files
• fires with mv scheduled -> sent and writes hey through a fake outbox
• cancels with mv scheduled -> cancelled
• makes STOP durable and cancels all pending events for that principal
• keeps same-time events distinct and survives separate process invocations

Executable acceptance passes for durable REMIND, ECHO, CANCEL, STOP, multiple users, unknown callers, restart persistence, and deterministic rejection of casual language.

The runner is UTC-only in this first slice. No paid provider, real number, LM, ICU, Unix-account mapping, daemon, or OS rewrite is included.