fix(web): de-ugly the Tier-3 persona pane — clear message instead of bare HTTP 404

persona_state hard-404s every Tier-3 (colon-id) agent by design upstream
(WT api.py:1220, "Phase 2.0 has no Tier 3 persona") — so the Persona pane
showed "persona not available (HTTP 404)" for consumer-defined characters.
loadPersona now reads error_code + renders a clear Tier-3-aware message
(she still responds in character; only the affect/OCEAN readout is gated),
with distinct text for persona_not_configured / 403 / other.

Also (snapshot): sindra switched to thoughtful-character role
(mistral-small-4-reasoning); worldtree-dev pinged re Tier-3 persona_state
roadmap (thread 01KVCR6P); #17 (bifrost-binding the chat client) teed up as
the next-context target.

v0.17.7

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "ratatoskr"
-version = "0.17.6"
+version = "0.17.7"
 description = "Worldtree Conversation API debug TUI — multi-pane observability dashboard"
 readme = "README.md"
 requires-python = ">=3.12"