fix: harden ssh script shell compatibility

scripts/src/help.ts

@@ -27,7 +27,7 @@ export function rootHelp(): unknown {
       { command: "ssh <route> upload <local-file> <remote-file> | ssh <route> download <remote-file> <local-file>", description: "Transfer whole files through SSH passthrough with remote temp files, byte-count checks, SHA-256 verification, and client-side chunk fallback." },
       { command: "ssh <providerId> apply-patch-v1 [tool args...] < patch.diff", description: "Fallback to the injected legacy remote apply_patch helper directly over SSH passthrough and stream the patch from local stdin." },
       { command: "ssh <providerId> py [script-args...] < script.py", description: "Run remote Python from local stdin through SSH passthrough without nested shell quoting; extra args become script argv." },
-      { command: "ssh <providerId> script [--shell sh|bash] [script-args...] <<'SCRIPT' ...", description: "Run a remote shell script from local stdin using shell -s; the default sh inherits provider proxy env, so --shell bash is only for bash-specific syntax." },
+      { command: "ssh <providerId> script [--shell sh|bash] [script-args...] <<'SCRIPT' ...", description: "Run a remote shell script from local stdin using shell -s; default sh inherits provider proxy env and gets the portable printf helper used by shell/script." },
       { command: "ssh <providerId> skills [--scope all|wsl|windows] [--limit N]", description: "Discover WSL/Linux and, for WSL providers, Windows skill directories in one SSH passthrough call." },
       { command: "ssh <providerId> find <path...> [--max-depth N] [--type d|f|l] [--contains TEXT] [--iname PATTERN] [--limit N] [--sort]", description: "Run a structured remote find command without nested shell quoting or parentheses." },
       { command: "ssh <providerId> glob [--root DIR] [--pattern PATTERN] [--contains TEXT] [--type any|f|d] [--limit N] [--sort]", description: "Run remote glob matching through the injected helper without shell glob expansion." },
@@ -189,6 +189,7 @@ export function sshHelp(): unknown {
       "For non-interactive remote commands, prefer argv for a single process and script/stdin for shell logic.",
       "For one-line remote shell logic without a heredoc, use `script -- '<command && command>'`; outer shell operators written outside tran, such as `tran G14:/repo sed ... && sed ...`, are parsed by the local shell before UniDesk starts and therefore cannot be redirected by the CLI. The explicit `shell '<command>'` operation remains available for the same sh -c path.",
       "When a one-line shell command is easier to type through the script path, `script -- '<command && command>'` runs that single string through the remote shell without waiting for stdin. When `script --` is followed by multiple tokens, it stays a direct argv form for commands such as `tran D601:/work script -- sed -n '1,20p' file`.",
+      "script and shell helper modes inject a tiny POSIX-compatible printf wrapper before user shell text, so portable printf headings such as `printf \"--- section ---\\n\"` work consistently under dash/sh and bash. Direct argv commands are unchanged.",
       "For arbitrary stdin streams into a workload command, use a workload route plus `exec --stdin -- <command> ...`; this keeps the route as location-only and avoids heredoc/base64/tar shell wrapping.",
       "`apply-patch` is the default remote text patch entry and uses the v2 local line-based patch engine with remote read/write operations, including Windows routes such as `D601:win/c/test`, so long Unicode/Chinese lines and pure insertion hunks avoid the legacy remote shell hunk parser.",
       "`upload` and `download` are the default whole-file transfer entries for non-text and generated files. They write through remote temp files, verify byte count and SHA-256 on both sides, and fall back from a single stdin payload to bounded client-side chunks before treating provider-gateway limits as a server-side problem.",