Fix/viewer stability

[PaoloC68]

This PR fixes five distinct bugs that together cause the CamoFox VNC viewer iframe to disappear, reload every few seconds, and steal keyboard focus from the Agent Zero chat input — eventually making the WebUI unusable until the plugin is disabled. All five are reproducible on a fresh install of Agent Zero + this plugin.

Debugged collaboratively with a user on a long session; root-causes traced end-to-end with server logs, state file inspection, and live DevTools console probing. Each commit is self-contained and explains its own fix.

Bugs fixed

1. execute.py — silent CLI helper fallback (commit d87f44a)

When execute.py runs outside /[a0](https://helpa0.com/#) as cwd, from usr.plugins.camofox_browser.helpers.cli import resolve_camofox_command fails silently and falls back to a stub that always raises RuntimeError("CamoFox CLI helper unavailable"). Setup step 7 fails with no useful diagnostic. Fix: prepend /[a0](https://helpa0.com/#) to sys.path before the import.

2. viewer_url.py — vnc_session_key derived from timestamp (commit 92aa7b3)

vnc_session_key = int(vnc_ts * 1000) changes on every set_vnc() write. The WebUI store uses session_key to detect real session changes — a timestamp-based key defeats this and causes the iframe to be reloaded on every 3-second poll, generating a new signed JWT each time. Fix: hash the raw upstream URL — session_key now represents session identity.

3. state.py — _normalize_entry clearing live vnc_url after idle TTL (commit 815a6b4, part 1)

The worst of the bunch. _normalize_entry() wipes vnc_url when vnc_age > _VNC_IDLE_TTL_SECONDS (10 s by default!) even though the camofox server's VNC stack is still running. The URL should reflect server reality, not a wall-clock heuristic. After 10 s of "idle" the iframe vanishes mid-session. Fix: remove the time-based clearing. URL changes only via explicit set_vnc() / clear_vnc().

4. state.py — get(user_id) strict per-user lookup (commit 815a6b4, part 2)

The WebUI has no agent context so resolve_user_id() returns "a0-default", while agent tools resolve to "a0-agent-N". Once the store caches _userId="a0-default", it keeps asking for that user even after browsing has moved to a0-agent-0. Result: empty vnc_url, no iframe. Fix: get() falls back to any active user when the requested one is idle.

5. camofox-store.js — showBrowser() toggles even when server already visible (commit d269c23)

if (this.vncUrl) return; is the only early-out. If the WebUI's vncUrl is null but the server is already in virtual mode, clicking the browser button triggers a full toggle cycle (stop VNC → close persistent context → relaunch → start VNC = ~3 s downtime) for no reason. Fix: if displayMode is virtual/headed or _rawVncUrl is set, just reveal the panel and force a poll.

6. camofox-browser-btn.html — iframe wrapped in x-if (commit a3111ce)

x-if destroys and recreates DOM on every state flip. During the inevitable null-URL gap on any toggle, the iframe is torn out of the DOM and the placeholder briefly flashes. When the URL returns, a fresh iframe is built, noVNC autoconnects, and the new iframe steals keyboard focus — making chat input impossible. Fix: use x-show for the iframe (DOM persists, only CSS toggles). Placeholder also gates on _rawVncUrl to suppress flashes.

Test plan

1. Fresh Agent Zero instance with this plugin enabled
2. Trigger any camofox_browse action → iframe should appear
3. Wait > 10 minutes idle → iframe should still be there
4. Send chat messages that trigger more browser actions → no focus loss, no "reload every 10 s" loop
5. Click browser icon while iframe is hidden → no toggle round-trip, panel reveals current session immediately

Notes for the maintainer

• The diff is small (~60 lines net) but each piece matters independently.
• I kept the legacy _VNC_IDLE_TTL_SECONDS constant since it's still used for browsing-staleness logic; just stopped using it to wipe URLs.
• Happy to split this into separate PRs if you'd prefer, but the bugs interact (fix: software rendering, Stop/Start buttons, VNC browser icon, and watchdog #2/Support for external CamouFox Server #3/Fix/viewer stability #4 are all reasons the iframe gets a null URL; #5/#6 are what makes that null URL catastrophic UX-wise).

CC: full debug session preserved if you want any specific scenario walked through.