PE-53 49 - #6

First tranche of Theme 4 (maintainability & test gaps), executed on current
main after Theme 1 and Theme 3 landed.

Test-gaps (characterization; each mutation-verified):
- runactions.test.ts — confirmCancelRun live-worker branch/copy, cancelRun +
  stopRunWorker in-flight tracking and finally-cleanup, tab: strip.
- agentcwdresolve.test.ts — resolveCwd block->tail->head precedence; head read
  fires only on a tail miss; null at the error boundary.
- pkg/jarvis/watcher_test.go + onexit_test.go — extracted pure predicates
  askAutoAnswerable (single single-select pre-filter) and optionIndexInRange
  (delivery bounds guard) from handleAsk (behavior-preserving) and tested them;
  outcomeSummary last-event-vs-task + 160-char truncation. wavetermdev#2 was unblocked by
  Theme 3 A1 (dac43d1).

Refactor wavetermdev#6 (behavior-preserving):
- findSessionTermBlock pure selector added to sessionviewmodel.ts; all 4
  duplicate "first term block with cmd:cwd" sites in sessionsidebarmodel.ts
  routed through it via a resolveTabBlocks id-resolver.

Deferred: wavetermdev#4 (runbody.tsx split) and wavetermdev#5 (agentsviewmodel.ts grid extract) --
pending the active Theme 2 work that edits those files.

Verified: vitest run (1138 pass), large-stack tsc (clean), go test
./pkg/jarvis/ (ok), go vet clean.

…t-scan brief

open-issues.md: add issue wavetermdev#6 (sealed Run-Evidence card, 6a/6b/6c). briefs: 2026-07-21 open-ended improvement-scan candidate backlog (its finding A3 is the read-pool work just landed).