feat(agents): pont Codex inter-agents + readiness/heartbeat lot 1

Deux chantiers livrés au vert (workspace entier : domain+application+
infrastructure 42 + app-tauri --lib 128, 0 échec).

## Codex inter-agents
- domaine: McpConfigStrategy::TomlConfigHome { target, home_env } +
  toml_config_home(...); AgentProfile::materializes_idea_bridge()
  (whitelist Claude/ConfigFile + Codex/TomlConfigHome); McpServerWiring
  + encodeur TOML.
- application: lifecycle apply_mcp_config bras TomlConfigHome (écrit
  {runDir}/<target>, pousse (home_env, parent) dans spec.env);
  guard_mcp_bridge_supported ré-exprimée via materializes_idea_bridge();
  catalogue Codex porte toml_config_home(".codex/config.toml","CODEX_HOME").
- app-tauri: is_codex_mcp_profile, migrate_codex_run_dir,
  mcp_server_entry_toml.
- tests: matrice domaine TomlConfigHome + round-trip dual Claude/Codex
  sur loopback réel (fakes, zéro token).

## Readiness/heartbeat lot 1
- domaine: readiness.rs — ReadinessPolicy::classify (Final => TurnEnded),
  variantes ReplyEvent::Heartbeat / ToolActivity.
- application: drain_with_readiness consulte la policy et appelle
  mark_idle sur le signal déterministe; branché dans ask_agent.
  Corrige la cause racine: une cible qui ne renvoie qu'un Final (sans
  idea_reply) débloque désormais sa file Busy.
- infrastructure: adapters de session émettent Heartbeat/ToolActivity.
- tests: drain_with_readiness_lot1 (points QA 5 & 6) verts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/app-tauri/src/chat.rs

@@ -175,11 +175,17 @@ impl ChatBridge {
 /// Maps a domain [`ReplyEvent`] to its wire [`ReplyChunk`]. Pure translation, no
 /// I/O — the single point where the typed turn event becomes a serialisable chunk
 /// (kept here so the pump and any test share one mapping).
+///
+/// Returns `None` for [`ReplyEvent::Heartbeat`]: a heartbeat is a non-terminal
+/// liveness proof (readiness/heartbeat lot 1) with **no chat content**, so it maps
+/// to no wire chunk — the pump simply skips it. Every content-bearing event still
+/// maps to exactly one chunk.
 #[must_use]
-pub fn chunk_from_event(event: ReplyEvent) -> ReplyChunk {
+pub fn chunk_from_event(event: ReplyEvent) -> Option<ReplyChunk> {
     match event {
-        ReplyEvent::TextDelta { text } => ReplyChunk::TextDelta { text },
-        ReplyEvent::ToolActivity { label } => ReplyChunk::ToolActivity { label },
-        ReplyEvent::Final { content } => ReplyChunk::Final { content },
+        ReplyEvent::TextDelta { text } => Some(ReplyChunk::TextDelta { text }),
+        ReplyEvent::ToolActivity { label } => Some(ReplyChunk::ToolActivity { label }),
+        ReplyEvent::Final { content } => Some(ReplyChunk::Final { content }),
+        ReplyEvent::Heartbeat => None,
     }
 }