rename the TIC system agent to event triage

TIC said nothing about what the agent does, and named the wrong thing: the
tick belongs to the scheduler, which is generic and lives outside it. The
agent's only decision is whether an incoming event deserves an interruption
— it sorts, it never acts — so it is now event-triage, matching the
functional naming of the two memory lints.

- agents/tic/ -> agents/event-triage/, module tic/ -> event_triage/,
  TicManager -> EventTriageManager, TicConfig -> EventTriageConfig
- agent id and chat source: "tic" -> "event-triage"
- config keys: tic.* -> event_triage.*, and the config.yml section tic: ->
  event_triage: (greenfield: previously set values fall back to defaults)
- i18n en/it/fr: Event triage / Triage eventi / Tri des evenements; dropped
  the stale "TIC sessions" mention from the debug-pages description
- docs/system-agents.md, docs/index.md, docs/settings.md, CLAUDE.md, SKALD.md

crates/skald-core/src/db/chat_sessions.rs

@@ -5,9 +5,9 @@ pub struct ChatSession {
     pub source:          String,
     pub agent_id:        String,
     /// True when a real user is actively participating (web, telegram).
-    /// False for fully automated sessions (cron, tic).
+    /// False for fully automated sessions (cron, event-triage).
     pub is_interactive:  bool,
-    /// True for short-lived task sessions (cron, tic) with no long-term
+    /// True for short-lived task sessions (cron, event-triage) with no long-term
     /// conversational value. May be used to skip memory / analytics sinks.
     pub is_ephemeral:    bool,
     /// Optional RunContext JSON blob assigned to this session.