AGENTS: Tell agents to not use mkosi box

It's easier to run the AI tool within mkosi box rather than telling
it to use mkosi box and forgetting to use it half the time.

AGENTS.md

@@ -14,15 +14,16 @@ Always consult these files as needed:
 
 ## Running arbitrary commands
 
-- Always run arbitrary commands with the `mkosi box -- ` wrapper command. This runs in an environment where more tools are available.
+- Never use `mkosi box` to wrap commands. You are either already running inside an mkosi box environment or
+running outside of it — use the tools available in your current environment directly.
 
 ## Build and Test Commands
 
-- Never compile individual files or targets. Always run `mkosi -f box -- meson compile -C build` to build
-the entire project. Meson handles incremental compilation automatically.
+- Never compile individual files. Always run `meson compile -C build <target>` to build the target you're
+working on. Meson handles incremental compilation automatically.
 - Never run `meson compile` followed by `meson test` as separate steps. Always run
-`mkosi -f box -- meson test -C build -v <TEST-NAME>` directly. Meson will automatically rebuild any required
-targets before running tests.
+`meson test -C build -v <TEST-NAME>` directly. Meson will automatically rebuild any required targets before
+running tests.
 - Never invent your own build commands or try to optimize the build process.
 - Never use `head`, `tail`, or pipe (`|`) the output of build or test commands. Always let the full output
 display. This is critical for diagnosing build and test failures.