fix(tui): rehydrate sessions after reconnect

[nxxxsooo]

Issue for this PR

Closes#32175

Type of change

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

What does this PR do?

The TUI could stop receiving events after a transient global SSE failure, and sessions already mounted before the gap remained stale after transport returned.

This change keeps those two concerns separate. The SDK provider retries rejected connections, iterator failures, and normal stream completion with bounded exponential backoff. Later server.connected epochs reconcile the authoritative session list/status and atomically refresh already-loaded session metadata, messages, parts, todo, and diff state. Confirmed deletions are pruned, failed hydration preserves prior state, and reconnect storms are serialized without overlapping passes.

This replaces #37957, which was automatically closed because its description did not use the required template sections.

How did you verify your code works?

• Transport regression suite: 15 pass, 0 fail.
• Reconnect coordinator: 6 pass, 0 fail; 120 pass across --rerun-each 20.
• Hydration suites: 16 isolated and 5 live tests pass.
• Full TUI package: 228 pass, 1 skip, 0 fail; package typecheck passes.
• Fresh arm64 native build from 00470701974fa23189a34c63f61b1932f2a4f394: SHA-256 a1ddeef525be970223b354706bf240728c07d961932a129b70bf2718c9c3953b.
• Two isolated proxy-gap cycles kept the same mounted attach PID, converged to direct REST state after restoration, and added exactly one server SSE lifecycle each. The second outage lasted 1.624 seconds, beyond the initial retry interval.
• The temporary session/processes were removed, QA ports were freed, and production was not contacted or modified.

Screenshots / recordings

Not applicable. This fixes transport and store reconciliation behavior; the runtime check asserted the mounted TUI pane title before, during, and after each gap.

Checklist

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

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