navi_code was systematically spawning sub-agents as `developer` instead of
itself, even though it already covers local code work. Root cause was a
three-channel nudge: the navi_code prompt recommended `developer` for "general
code work" and framed omit (-> navi_code) as the exception; spawn_agent's
description listed `developer` as the coding example and never mentioned
navi_code; the injected Available-profiles list shows developer's broad
"General-purpose software development" blurb. The planner locks profile_id at
plan time on those same signals, so the bias is baked in before execution.

Flip the default in all three places: for code work OMIT profile_id so the
sub-agent runs as the current profile (navi_code); set profile_id only for a
different specialisation (secretary/server_admin/tool_developer). developer is
not removed as a profile — it is just no longer recommended from navi_code.