control: file edit as a command — web editSubmit bypasses the registry #43

The web file editor (internal/httpd/accounts.go editSubmit) calls gitutil.CommitFileChange directly instead of dispatching a control command. The Parity page's own rule says web writes call the same control commands; this one doesn't, and the capability is unreachable from the CLI (without git push) and from the JSON API — so the iOS app cannot offer the web's "edit a file" row.

Proposal: repo commit-file <owner/name> <path> --ref <branch> [--message <m>] [--file -] (content on stdin, same discipline as other long inputs), refusing on protected branches, require-signed repos, and unverified primary email exactly as editSubmit does today — then editSubmit dispatches it.

Ref #11