fix(review): respawn the reviewer pane when the harness changes

[anuj7511]

Summary

After switching a project's reviewer harness (e.g. claude-code → opencode), a
new review reused the still-live pane from the previous harness — so the review
ran under the old harness's sandbox/permissions/env while the DB recorded
the new harness.

Root cause

The reviewer handle is stable per worker (review-<workerID>, independent of
harness), and Trigger reused any live pane keyed only on Alive — it never
compared the pane's harness to the freshly-resolved one. Reuse goes through
Notify, which only sends prompt text; sandbox/permissions/env are applied only
at Spawn. So a claude-code pane kept serving opencode-intended reviews.

Impact

Security-relevant: if you switch to a stricter reviewer (e.g. opencode's
deny-all-bash profile), that stricter sandbox is silently not applied until the
old pane dies. Reviews run under the previous harness's looser profile.

Fix

Gate pane reuse on the resolved harness matching the harness the live pane was
launched under; a changed (or unrecorded) harness respawns instead. Because the
handle is stable and tmux new-session collides on a live name, Spawn now
destroys any stale pane on that handle first (idempotent when absent), so the
switch actually replaces the process under the new harness's profile.

[somewherelostt]

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• @neversettle17-101
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