[TheGreatAxios]

Spawn timings for Linear CL-9019.

• setup_ms measures worktree/admission/lane setup before runSubAgent; setup failures report setup_ms elapsed to failure.
• Six tool family buckets (read/write/shell/search/agent/other) counted alongside tool_call_count; unknown tools fall into other so the bucket sum always holds.
• hydrate_ms times the attachment-rehydrate transform, including resume followups via the shared decorator closure.
• subagent_end allowlist gains the 8 numeric props; duration_ms semantics unchanged; no per-tool names emitted.

Verification: tsc clean on all touched files (repo-wide typecheck/build/tests blocked by pre-existing oauth-core skew in the shared node_modules, unrelated to this diff).

Fixes CL-9019

[linear-code]

CL-9019

[TheGreatAxios]

Closing as telemetry-only: does not improve operator-facing output, and the PR is not CI-green + trivial after the 0333 merge wave. Reopen if product telemetry is prioritized separately.