feat(agent): bind transport S-MCP — outils idea_* vivants de bout en bout (M5a-e) — §14.3.1

Dernier kilomètre de l'orchestration native : une CLI MCP réellement lancée
joint le serveur MCP du projet et ses outils idea_* aboutissent au vrai dispatch.

- M5a endpoint loopback par projet (interprocess UDS/named pipe, source unique
  mcp_endpoint, cleanup au close) — zéro port réseau, AppImage/SSH-safe.
- M5b sous-commande `idea mcp-server` : pont stdio↔loopback headless (avant init
  Tauri), handshake {"project","requester"}, endpoint-absent borné, EOF propre.
- M5c McpServerHandle boucle accept + serve_peer par pair ; requester réel
  propagé jusqu'à OrchestratorRequestProcessed (fin du "mcp" figé) ; isolation
  des pairs ; terminaison propre.
- M5d apply_mcp_config écrit la déclaration réelle (current_exe + --endpoint
  mcp_endpoint + --project simple-uuid + --requester) ; McpRuntime injecté comme
  donnée (application ne dépend pas de app-tauri).
- M5e smoke e2e sur vrai loopback : list/ask inline, cible PTY → erreur typée,
  JSON malformé → pas de panic, requester propagé.

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

crates/app-tauri/Cargo.toml

@@ -25,11 +25,18 @@ application = { workspace = true }
 infrastructure = { workspace = true }
 tauri = { workspace = true }
 tauri-plugin-dialog = { workspace = true }
-tokio = { workspace = true }
+# `io-std` (on top of the workspace features) gives the headless `mcp-server`
+# bridge access to `tokio::io::{stdin,stdout}` without widening tokio elsewhere.
+tokio = { workspace = true, features = ["io-std", "rt"] }
 serde = { workspace = true }
 serde_json = { workspace = true }
 thiserror = { workspace = true }
 uuid = { workspace = true }
+# Cross-OS local IPC for the MCP loopback transport (M5a): Unix domain socket
+# (Linux/macOS) + Windows named pipe behind one async API, no network port. Pulled
+# in only here (the transport is an app-tauri/infra concern); its `tokio` feature
+# keeps us off tokio's `net` feature workspace-wide.
+interprocess = { version = "2.4", features = ["tokio"] }
 
 [features]
 # Passthrough toggles to enable the real embedders in an IDE build. OFF by default