feat: switch index respects active filter

[cperalt]

Closes #29

[inspect-review]

inspect review

Triage: 1 entities analyzed | 0 critical, 0 high, 0 medium, 1 low
Verdict: standard_review

Findings (1)

1. [low] The comment says the "running" filter should include only sessions where an agent is currently running, but the implementation also includes status === "waiting" (and "tool-running"). Including "waiting" contradicts the stated semantics and will misclassify non-running sessions as running.
   Evidence in diff:
   // "running" — only sessions where an agent is currently running
   return st === "running" || st === "tool-running" || st === "waiting";

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Reviewed by inspect | Entity-level triage found 0 high-risk changes

[Palanikannan1437]

thanks @cperalt for the pr!