CI flakes seen on #1463 (activity attribution wait, profile index timing, telemetry race, scope latency)

[Dumbris]

These tests failed CI on PR #1463 at head 0edf3da and passed when rerun. None of them is related to that PR's change. They were all seen on slow or shared runners.

• TestActivityAttribution_InternalToolCallReadsSessionResolution (internal/server/activity_attribution_sources_test.go:155), Windows: the 5 s require.Eventually waiting for the asynchronous activity record expires. Sibling tests on the same runner took up to 43 s. Widen the wait in the activity-attribution tests, or wait on a deterministic signal instead.
• TestRetrieveTools_ProfileWidenedByRawApplyIsSearchableImmediately (internal/server/retrieve_tools_profile_index_reload_test.go:126), shuffle lane: this one returned nil hits once, after 9.6 s. It didn't reproduce with the CI seed or under load, so it is likely timing.
• Shuffle lane: a telemetry DATA RACE in TestPayloadV13_PassesScanWithCommonUsernameBlocked.
• FR-011 merge-base regression: TestScopeLatency_ReadCache_ScopedVsAdmin, where the scoped read_cache p95 gap was 29.6 ms against a 20 ms budget on a shared runner.