feat(custom-model): show real-time llama.cpp backend status in the loading banner

Answers the underlying request behind investigating llama.cpp log
access: surface what the backend is actually doing, live, on top of
the existing countdown timer during a model load.

- getLatestLlamaSwapLogLine()/pruneIdleLlamaSwapLogTails()
  (custom-model-routes.ts): one persistent GET /api/events (SSE)
  connection held open per endpoint, parsing logData frames and
  keeping the latest source:"upstream" (backend llama-server) line —
  filtering out llama-swap's own source:"proxy" request-access lines.
  Idle-closed after 30s of no polling, same 20s sweep as the existing
  swap-displacement check.
- running-status route now returns logLine alongside the existing
  isLlamaSwap/running fields.
- Frontend: _watchLlamaSwapLoading's banner gains a second line
  ("llama.cpp: <line>", bootlog timestamp/level/component prefix
  stripped for display) that stays on the last real thing llama.cpp
  said rather than clearing to blank between polls.

⚠️ Caught and fixed before merge, not after: the first cut targeted
GET /logs (the endpoint the name suggests), shipped a working-looking
implementation with passing tests, and only failed a live check against
the real Nemesis llama-swap deployment — /logs turns out to carry ONLY
llama-swap's own proxy request-access log and never once showed a
single backend line, even seconds after a real, confirmed model swap
triggered via a direct API call. GET /api/events's logData frames
(with an explicit source field distinguishing upstream from proxy) are
the only source that actually has backend output; corrected and
re-verified live end-to-end through an actual forced swap before
writing this commit, confirmed live to hold its connection open
indefinitely (unlike /logs, which closes after a fixed ~100KB).

12 tests for the corrected /api/events parsing (SSE frame buffering
across chunk boundaries, source filtering, malformed/wrong-type frames,
connection reuse, idle pruning) plus 2 for the frontend banner
rendering. Typecheck/lint/frontend-syntax clean; full suite shows no
new regressions (14 more passing than baseline, matching the new
tests; same pre-existing Windows-environment failures).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RqZeHrRS6DYcGcGX2p9EwG

.changeset/run-menu-custom-model-picker.md

@@ -19,6 +19,8 @@ Two more, from actually clicking through the swap-confirm and context-warning di
 
 - **A session's model getting silently swapped out later, not just at launch.** The conflict check above only ever runs at the moment a session is created or a model applied — confirmed live: a second Codex session picking a different model launched with no warning at all, because nothing conflicted at that exact instant, yet it silently evicted the first session's model regardless (llama.cpp runs one model at a time). There was no mechanism to catch a swap caused by a DIFFERENT session's own later, ordinary use. A new periodic sweep (`detectCustomModelSwapDisplacements`, every 20s, one `GET /running` per distinct endpoint with a live custom-model session) now compares each such session's own model against what's actually loaded, and a new `custom-model:swapped-out` SSE event drives a global toast naming the displaced session and what's now loaded instead — so you find out before typing into a session that's about to trigger yet another reload. Notifies once per displacement, clearing once a session's own model is loaded and ready again so a later, genuinely new displacement notifies again.
 
+- **The loading banner's second line is now the real backend log line, not just a countdown.** llama-swap's `GET /api/events` SSE stream carries the actual `llama-server` process's own stdout (`load_model: loading model '<path>'`, `llama_server: model loaded`, tokenizer warnings, all of it) tagged `source: "upstream"`, distinct from llama-swap's own `source: "proxy"` request-access lines — confirmed live end-to-end through a real forced swap, and it correctly stays on the last thing llama.cpp said once the load goes quiet rather than clearing to blank. ⚠️ This feature's own first cut targeted `GET /logs` instead (the name that suggested it) and shipped a live-tested implementation against it before this live check caught that `/logs` carries ONLY the proxy request log and never once showed a single backend line, even seconds after a real, confirmed swap — corrected before merge, not after.
+
 Remote (SSH) and Docker sessions are refused for now (400) — their restart reattaches the durable remote/in-container tmux rather than relaunching the agent.
 
 **One more, from watching it launch live: opencode, Codex, Gemini, Pi, Grok, DeepSeek and OMP now launch directly on the endpoint, with no restart at all.** Picking one of these seven from the Run-menu picker used to launch natively first, wait for it to settle, then restart it in place with the endpoint applied — a deliberate two-step design, but visibly a native boot immediately followed by a second one, worst on a CLI whose TUI fully reinitializes on a restart (confirmed live on Codex). `POST /api/quick-start` now accepts a `customModel` field and computes the same injection _before_ the session exists, launching straight onto the endpoint the first time — no visible relaunch, and it also runs the same llama-swap conflict check (warns before unloading a model another live session is using) at create time. Claude still uses the original launch-then-restart path for now (its own `--resume`-based restart is far less jarring, and `runClaude()`'s multi-tab and docker-config-drift-retry logic make folding it into the one-shot path separate work).