[quality] test: pin the poller-to-thrash-breaker wiring end to end (src/pkg/agent pollTmuxOutputForAgent → checkBlockedThrash)

[kubestellar-hive]

Test Improvement

Adds src/pkg/agent/thrash_poller_wiring_test.go with one end-to-end case, TestPollTmuxOutputForAgent_WiresThrashBreaker:

• Seeds a real (hermetic-harness) tmux pane, starts pollTmuxOutputForAgent, waits for the first capture so the diff baseline exists.
• Injects a burst of git push blocked: lines past the thrash threshold (5 in 60s).
• Asserts the agent ends up paused with trigger thrash-breaker — the pause, not a log line.

Why: checkBlockedThrash/recordBlockedAndCheck are unit-tested, but the single call in the poller (manager_poll.go:244) that makes the breaker fire in production had no test — the exact #6147 shape (a correct breaker nothing invoked). A poller refactor could drop that line with every existing test still green.

Verification:

• Passes on v5; ran -run 'Thrash|PollTmuxOutput' -count=3 — all green (~6.6s per run for the new test).
• Mutation-checked: deleting the m.checkBlockedThrash call in the poller makes exactly this test fail.

Note: the test uses a 220-column tmux session — capture-pane returns wrapped display lines, and at 80 columns the marker wraps mid-word ("git push bl / ocked:"), invisible to the breaker's Contains match. That wrap-sensitivity of the marker match in production is recorded as a separate advisory bead.

Claimed ground: src/pkg/agent/thrash_poller_wiring_test.go (new file only); pins pollTmuxOutputForAgent → checkBlockedThrash wiring. Disjoint from open PRs #6328 (pkg/proxy), #6327 (pkg/hub), #6323 (docs), #6292 (claude write roots).

Related Issue

Fixes #6297
Refs #6147

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Filed by quality agent (hold-gated mode). Human review required.

— hive: agent=quality backend=copilot model=claude-fable-5

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