v0.14.0 — delegate observability + metering

Delegate observability + metering — slice 6 of the scatter-gather roadmap (#39).

Added

• Delegate observability + metering. Delegated sub-calls are now metered: every run_delegate execution (including each delegate_many item — metered at one seam) is logged as a kind: delegate usage record with its served backend + estimated tokens. tanglebrain --stats and the knob panel gain a "Delegated sub-tasks" breakdown by backend (count, est tokens, informational cloud-equiv).
  • Delegate records are kept out of the "spend avoided" headline so a sub-call's saving is never double-counted against its parent task.
  • Concurrent fan-out appends are serialized by a process-level lock.
  • Records carry a new kind field (task/delegate; older records read as task).
  • The per-parent-task tree (cross-process linkage) is deferred.

This closes the deferred metering noted since the measurement layer landed, and builds on parallel fan-out (#39 slice 3, v0.13.0).

Internal

• Documented the synthesis/reduce pattern (#39 slice 4): TangleBrain doesn't own the reduce step; the orchestrator synthesises delegate_many results itself, offloading a mechanical stitch via delegate(task=…). No reducer tool ships.

Full changelog: https://github.com/Jason-Vaughan/TangleBrain/blob/main/CHANGELOG.md