Exec/ACP: inject OPENCLAW_SHELL into child shell env (#31271)

* exec: mark runtime shell context in exec env

* tests(exec): cover OPENCLAW_SHELL in gateway exec

* tests(exec): cover OPENCLAW_SHELL in pty mode

* acpx: mark runtime shell context for spawned process

* tests(acpx): log OPENCLAW_SHELL in runtime fixture

* tests(acpx): assert OPENCLAW_SHELL in runtime prompt

* docs(env): document OPENCLAW_SHELL runtime markers

* docs(exec): describe OPENCLAW_SHELL exec marker

* docs(acp): document OPENCLAW_SHELL acp marker

* docs(gateway): note OPENCLAW_SHELL for background exec

* tui: tag local shell runs with OPENCLAW_SHELL

* tests(tui): assert OPENCLAW_SHELL in local shell runner

* acp client: tag spawned bridge env with OPENCLAW_SHELL

* tests(acp): cover acp client OPENCLAW_SHELL env helper

* docs(env): include acp-client and tui-local shell markers

* docs(acp): document acp-client OPENCLAW_SHELL marker

* docs(tui): document tui-local OPENCLAW_SHELL marker

* exec: keep shell runtime env string-only for docker args

* changelog: note OPENCLAW_SHELL runtime markers

docs/web/tui.md

@@ -113,6 +113,7 @@ Other Gateway slash commands (for example, `/context`) are forwarded to the Gate
 - Prefix a line with `!` to run a local shell command on the TUI host.
 - The TUI prompts once per session to allow local execution; declining keeps `!` disabled for the session.
 - Commands run in a fresh, non-interactive shell in the TUI working directory (no persistent `cd`/env).
+- Local shell commands receive `OPENCLAW_SHELL=tui-local` in their environment.
 - A lone `!` is sent as a normal message; leading spaces do not trigger local exec.
 
 ## Tool output