mu 3.11.0

The skill learns model tiers, and a review panel's fixes land. A new
recipes/models.md says which model tier each role needs; a five-angle
review of the skill found 41 problems, and the confirmed ones are fixed.
mu agent close no longer deletes edits in a cp -a workspace, and
mu agent send to a dead pane says so.

Upgrade with npm i -g @mu-crew/mu@3.11.0, then /reload in running pi
sessions to pick up the skill. No schema change.

Changed

• Skill: one agent per ready task, not per track. An umbrella puts
  every unit on one track, so "one agent per ready track" read literally
  ran a fan-out with one worker. The skill now says to spawn per ready
  task, and to chain tasks that share files with block so only one is
  ready at a time.
• Skill: wording fixes. REFUTED is the verdict that sends a brief
  back for rewrite (there was no AMEND); SKILL.md drops text that
  restates --help and the outside-pi spawn steps, uses VOCABULARY
  terms, and models, worker and brief recipes get checkable Done whens.
• Skill: model tiers. New skills/mu/recipes/models.md ranks models
  by position in a lab's lineup (frontier, strong, mid, cheap, local),
  says which roles need which tier, and keeps local models as a last
  resort. Checkers run at the tier of whoever wrote what they check, or
  higher, from another family. SKILL.md and ten recipes point at it in
  place of the pi_mini/pi_big keys. Skill-only: /reload in running
  pi sessions to pick it up.

Fixed

• Skill: review recipes keep blockers honest. UNVERIFIED findings
  no longer contradict --if-ready (umbrella stays open);
  adversarial-review re-blocks downstream work on review_x_2 after a
  rejection; findings Group blocks the umbrella on the fix before
  superseding; adversarial-review uses finding and scopes itself to
  commit-producing units; rules-audit splits delegate/workstream mode;
  tasks-or-calls defines delegate call for scratch and a satisfiable
  Done when.
• Skill: drift-audit and recovery. The drift-audit late-note query
  no longer hides an unrelated CLOSE: note that follows a close;
  recovery's Done when is per operation and reachable on the DRIFT path;
  its teardown/undo bullets keep only what --help lacks.
• Skill: codemode driver. The scratch script writes each note to a
  file and pipes it to mu task note, so answer text (e.g. a MU_EOF
  line) never runs as shell; the stale cap-refusal warning points to
  orchestrator-loop § Concurrency.
• Skill: remote-workers recipe safety. Poll only after the worker
  reports done (the poll closes the task); gate on a scratch checkout
  via a temporary ref, never main; --after-runs takes the send's
  runs unchanged; no blanket pkill -f x2ssh.
• mu agent close no longer deletes cp -a workspaces silently. A
  none-backend workspace can't prove it is clean, so close refuses
  (WorkspacePreservedError) unless --discard-workspace. SKILL.md and
  waves.md now give the safe workspace free path and the refresh --from fix for unpushed merges.
• model examples with :<level> failed through a gateway
  provider. pi reads the first segment as the provider, so
  anthropic/…:high died with "No API key". The models recipe, delegate
  guide and mu_delegate help now say to copy <provider>/<model> from
  pi --list-models; a test pins that mu_delegate accepts
  provider/family/id:level.
• mu agent send to a dead pane no longer says "ctl: refused". When
  the control socket is silent and the pane is gone (the CLI exited,
  e.g. no API key), ctl verbs now raise AgentPaneDeadError with next
  steps to read the log, close the row and respawn, not link/kick/ssh
  advice. A live pane whose socket refuses still raises
  AgentCtlUnreachableError.