test(tauri): on-device DNS-SD verification runbook + Test-tab checks (#334)

[momics]

Stacked on momics-interop-test-harness-tab (draft PR #343, the #340 Test tab). Base this PR on momics-interop-test-harness-tab, not main.

Why

The #330 DNS-SD standardization landed mobile-native Tauri plugin code that no CI job compiles or runs (no iOS/Android runner). Two of those changes are review-only defect fixes needing on-device confirmation:

• Android serialized resolve queue (IrohHttpPlugin.kt) — NsdManager.resolveService() allows one outstanding resolve; concurrent calls previously failed FAILURE_ALREADY_ACTIVE and silently dropped records.
• iOS re-emit on record change (IrohHttpPlugin.swift) — dedup changed from one-shot Set<String> to [String: DnsSdRecordSnapshot] (snapshot = TXT + addrs).

An automated session can't press buttons on hardware, so this PR delivers the tooling for the operator's real-device pass.

What

Runbook — docs/internals/dns-sd-device-verification.md: each of the 6 acceptance criteria → concrete Test-tab steps → exact greppable IROH_DNSSD_CHECK / native pass-fail signatures, a device/OS results matrix ready to paste into #334, and follow-up-issue filing guidance. Linked from the internals README.

Test-tab affordances (opt-in, dev-only, force-stopped on page teardown; new cards, no regression to the existing Test flow):

• browsePeers() isActive transition watch — criterion 2
• multi-service burst advertise/browse for the Android resolve queue — criterion 3
• live TXT/port mutate control for the iOS re-emit dedup — criterion 4
• greppable port/host logging on the generic browse loop so iOS metadata-only (port=0, host=undefined) is directly confirmable — criterion 5

Native additive log lines (same IROH_DNSSD_CHECK prefix, log-only): Kotlin drainResolveQueue (dequeue/resolved/failed + queue depth) and the Swift re-emit branch (new vs reemit + rev).

Key finding

iOS dedups on a TXT + addrs snapshot (its generic browse never resolves an endpoint, so port is always 0). A port-only change is invisible on iOS — the re-emit trigger must be a TXT change. Documented in the runbook; the mutate control bumps a TXT rev (and toggles port for Android's benefit).

Verification (local)

• cargo check -p iroh-http-core and the tauri plugin crate — clean
• npm run build:shared then npm run typecheck (shared/node/tauri) — clean
• example vite build — succeeds (26 modules)
• example tsc — only 3 pre-existing errors, none in the new code

Native plugin edits are additive log-only (no CI compiles them). Criteria 1–5 are only satisfied by the operator's on-device pass — this PR makes that pass runnable and unambiguous.

Refs #334

[momics]

Superseded by the consolidation PR #350, which was built from the device-validated integration branch and folds this work in. Closing to reduce review noise — the branch and its commits remain intact as the regression-first record, and can be reopened if needed. All fixes here are verified present in #350 (which is CI-green and device-tested).