fix(tui): desynchronize managed reconnect ensure herd

[armancharan]

Issue for this PR

Related to #36285

#36285

Parent epic: #36441

Builds on ○ #37585 (stream ownership / post-ensure jitter) and ○ #37570 (ensure-on-first-failure). This PR is the reconnect-herd slice only — update/replacement UX and cold-location cost remain out of scope.

✧ raised · ○ in review · ● approved · ✓ merged

#36441 epic: scope streams + bound payloads

Merge in order:
v2
└ ○ #37486 location interest
   └ ○ #37487 session interest + fan-out bench
      └ ○ #37585 stream ownership / diagnostics
         └ ○ #37586 reconnect herd ← this PR

Siblings under the epic (not git parents of the stack tip):
└ ○ #37559 session blobs + payloadHash
└ ○ #37570 ensure-on-first-failure → feeds #37586

Stacked on #37585 (event-stream-ownership). GitHub base is v2 because the parent branch is fork-only; herd-only diff: armancharan/opencode@event-stream-ownership...reconnect-herd — retarget base onto that branch after #37585 merges.

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

N TUIs reconnecting after a managed-service restart were calling Service.ensure in lockstep (attempt 1 skipped backoff), launching many serve --service contenders together.

• Pre-ensure spread: 0..500ms jitter before every service.reconnect() / ensure so callers desynchronize
• Keep ensure-on-first-failure: after the spread, attempt 1 still ensures immediately and skips the post-ensure 1000+jitter backoff when ensure succeeds
• Export ServerConnection.managedReconnect + regression tests (aligned with test(cli): lock managed reconnect ensure-on-first-failure #37570) plus a seven-caller concurrent reuse test that must not spawn

How did you verify your code works?

• packages/cli test/server-connection.test.ts — ensure-on-first-failure; version reuse; concurrent reconnects reuse one endpoint without spawning
• packages/tui test/cli/tui/reconnect-herd.test.ts — ensure spread / backoff bounds
• packages/tui test/cli/tui/use-event.test.tsx — attempt-1 ensure still happens after spread; cleanup aborts in-flight ensure
• typecheck in packages/cli and packages/tui

Acceptance → test

Claim	Test
Ensure spread desynchronizes reconnecting clients	ensure spread stays within jitter bounds and desynchronizes samples
Post-ensure backoff stays in [1000, 1500)	post-ensure backoff stays in [1000, 1500)
First reconnect still ensures (after spread)	backs off when a resolved event stream keeps failing + managed reconnect ensures the service on the first failure
N concurrent reconnects reuse healthy endpoint without spawn	concurrent managed reconnects reuse one healthy endpoint without spawning
Healthy mismatched version reused under reconnect	managed reconnect reuses a healthy service from another version

Screenshots / recordings

N/A — not a UI layout change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

Made with Cursor

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