docs(tracker): B6/B7/B12/B13/B15/B16 root causes + fix plans

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/production-quality/TRACKER.md

@@ -155,6 +155,20 @@ All backlog bugs now mirrored as Gitea issues: B1→#8, B2→#9, B3→#10, B4→
 
 **B14 cloud browse Tor-not-FIPS** — ROOT-CAUSED (nuance). FIPS-first logic WORKS (`fips/dial.rs` send_get :331 tries FIPS, falls back to Tor on 404/5xx; v1.7.94 fix). BUT the 4 content handlers in `api/rpc/content.rs` (browse :297, download :237, download_paid :356, preview :421) capture `_transport` and NEVER call `record_peer_transport()` → UI badge shows Tor/null even when FIPS used. FIX: add `record_peer_transport(data_dir, None, Some(onion), &transport.to_string())` after each successful send_get (storage.rs:84 has the fn). ⚠️ VERIFY on nodes whether FIPS is ACTUALLY used or genuinely falling back to Tor (if genuinely Tor, deeper FIPS-reachability issue beyond recording). TEST: after browse, last_transport = fips (when peer FIPS-reachable).
 
+## INVESTIGATION FINDINGS 2026-06-15 (B6/B7/B12/B13/B15/B16) — cutoff insurance
+
+**B13 Fedimint CSS** — app HTML (docker/fedimint-ui/index.html) uses absolute /assets/* paths; under /app/fedimint/ the browser requests /assets/* which hit the main SPA, not :8175 → unstyled. FIX: nginx sub_filter rewrite (same proven pattern as indeedhub/botfights blocks) in image-recipe/configs/nginx-archipelago.conf (/app/fedimint/ ~:641) + snippets/archipelago-https-app-proxies.conf (~:164) + bootstrap patch for existing nodes. Rewrites href/src/url '/' → '/app/fedimint/'. TEST: curl .../app/fedimint/assets/...css → 200 real CSS.
+
+**B6 ElectrumX archival gate** — electrs needs a NON-pruned full node; install card doesn't warn at a glance. /bitcoin-status returns blockchain_info.pruned. Yellow badge pattern exists (MarketplaceAppCard.vue). FIX (frontend, simple): show a yellow "Requires a full archive Bitcoin node (not pruned)" note on the electrumx card (MarketplaceAppCard.vue ~:53). catalog.json electrumx already has requires. 
+
+**B7 ElectrumX stuck loader** — sync overlay gated by electrsSync (useElectrsSync.ts syncing = status!=='synced'); if status never flips to 'synced' (stale/crash) the overlay blocks the UI forever. AppSessionFrame.vue:44 iframe gate `!electrsSync`. FIX (frontend): fail-open — allow iframe when electrsSync?.stale (and add a timeout in useElectrsSync.ts so a slow/stale status stops blocking after ~5min). 
+
+**B15 bitcoin sync UI lag** — Home.vue:485 polls every 30s. FIX: faster bitcoin refresh (~5-10s) (separate interval for bitcoin vs system stats).
+
+**B16 bitcoin status vanishes** — homeStatus.ts refreshBitcoin clears/leaves bitcoinAvailable null on a failed/transitional poll → HomeSystemCard.vue:60 v-if hides the card. FIX: retain last-known bitcoinAvailable on transient failure + show an "Updating…" badge instead of disappearing.
+
+**B12 mempool not connecting** — stacks.rs:1278 + apps/mempool-api/manifest.yml:50 hardcode CORE_RPC_HOST=bitcoin-knots; on nodes running bitcoin-core (not knots) mempool-api gets getaddrinfo ENOTFOUND bitcoin-knots. Also ELECTRUM_HOST=electrumx absent on pruned nodes (docs/CONTAINER_LIFECYCLE_HANDOFF.md:654). FIX: detect which bitcoin container runs (knots vs core) + set CORE_RPC_HOST dynamically; qualify the mempool stack so it doesn't half-start without electrumx. Backend (stacks.rs) — medium risk, test on .116.
+
 ## Progress log
 - 2026-06-15: tracker created. v1.7.96-alpha shipped. All 19 bugs filed as Gitea issues #8–#26. vps2 feature issues (G#3/5/6) deferred (no new features).
 - 2026-06-15: **B5 (LND CORS) ✅ DONE** — root-caused, both fixes implemented, verified on .116/.198/.103 (harness 4/4 each), committed `1db720af`, pushed to vps2 main. Will bundle into .97 (Gitea #12 to close on .97 ship).