test(plugin): wait for the v2 lazy-refresh tier instead of sleeping past it

[diegosouzapw]

Fixes a pre-existing race in the opencode plugin v2 suite. Surfaced by #12965 —
that PR is a dependency bump and does not cause this; it is simply the first PR
in a while to touch @omniroute/opencode-plugin-v2/, which is what makes the job
run at all.

The race

lazy refresh: [m1] then [m1,m2] reloads once; identical runs never reload waits
for the plugin's asynchronous optional tier with a fixed await sleep(5). When
the tier lands after that sleep, its reload is still pending and the next
assertion counts it:

✖ lazy refresh: [m1] then [m1,m2] reloads once; identical runs never reload
  AssertionError: an identical run never reloads
  2 !== 1

The file fails on every isolated run against the current release/v3.8.51
tip, with no changes applied. It only passed when the whole suite ran together
and unrelated work happened to give the tier enough slack — which is why the
green local npm test and the red CI job disagreed.

The fix

Both sleeps become await settle(() => reloads): poll until the observed value
holds steady for three consecutive turns, with a 5s ceiling. The wait now tracks
the work instead of the clock. The assertions themselves are untouched —
this changes how the test waits, not what it verifies.

Why nobody saw it

.github/workflows/opencode-plugin-ci.yml filters on

paths:
  - "@omniroute/opencode-plugin/**"
  - "@omniroute/opencode-plugin-v2/**"

so Test v2 only runs when those directories change. The nightly release-green
sweep never triggers it, and the failure stayed off the base-red radar.

Validation

Check	Before	After
tests/index.test.ts isolated, 6 runs	0/6 green	6/6 green
full v2 suite (npm test)	218/218	218/218
npm run build (tsup)	pass	pass
prettier --check	—	clean

Diff is one file: @omniroute/opencode-plugin-v2/tests/index.test.ts.

⚠️ base-red inherited: #12732 — release/v3.8.51 is not green; any failing
check outside Test v2 on this PR comes from the tip, not from this branch.