Narrows the push row to a human invocation

[johnnyt]

Why

The git push, gh pr create row of the agent-authority table said that
invoking /wurk:mr itself satisfies the user's ask, so the skill does not
stop to ask again. The anti-inference paragraph merged into the same section
in 86877d0 says the opposite for the relayed case: a dispatch from a
conductor, an orchestrator or a parent session is not by itself the user's
ask.

Both cannot hold. If invoking the skill satisfies the trigger, a conductor
dispatching a worker that runs the skill has satisfied it without the user
saying anything - the self-authorizing path the anti-inference paragraph
exists to close. Two agents in a sibling repo read this prose and reached
opposite conclusions about whether they could push.

The row's still-unauthorized cell shows the original intent: it guards
against inferring permission from having finished work. It was written for a
human typing the skill name, before orchestrated campaigns existed.

What

One line, the trigger cell of that one row. It now says who may invoke the
skill:

• a human invoking /wurk:mr satisfies the trigger, so the skill does not
  stop to ask again - the no-double-asking convenience is unchanged for the
  case it was written for;
• a conductor, an orchestrator or a parent session invoking it on the user's
  behalf does not, and needs the campaign's consent.

This is a narrowing. The still-unauthorized cell is untouched, and no other
row changes.

Notes

• Gate: gate.rb reports applicable: false - the diff is CLAUDE.md only,
  nothing under lib/, test/, config/, mix.exs, mix.lock. That is
  the commit row's own "a change touching no Elixir code has no gate to run
  and may commit on review of the diff alone". mix quality --profile merge
  ran anyway, unconditionally per .claude/wurk/mr.md, and was green through
  every stage; the ADR judge skipped cleanly, since CLAUDE.md is not one of
  its judged scopes.
• No changelog fragment: agent-authority prose is invisible to a caller of
  the public API.
• The installed wurk:mr skill still states the old rule in its own preamble
  ("invoking /wurk:mr is that gate firing"). That text lives outside this
  repo and is out of scope here, but it now lags this row.

Closes st-phmi