feat(tickets): création d'un assistant IA de ticket (backend + frontend)

Ajoute le chat assistant IA attaché à un ticket (#8).

Backend Rust :
- use cases OpenTicketAssistant/CloseTicketAssistant + tests
- politique d'outils par agent (domain/agent_tool_policy) et policy MCP
- store de contexte assistant + gabarit default_ticket_assistant.md + tests
- events TicketAssistantOpened/Closed
- commandes Tauri open_ticket_chat/close_ticket_chat et câblage state/lib/events

Frontend :
- gateway (ports, adapters ticket + mock, domain)
- hook useTicketAssistant + composant TicketAssistantPanel
- intégration dans TicketDetail

Tests verts : vitest tickets.test.tsx (23), cargo test application::ticket_assistant (1),
infrastructure::assistant_context_store (2).

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

crates/infrastructure/src/orchestrator/mcp/mod.rs

@@ -29,6 +29,7 @@
 //! child process).
 
 pub mod jsonrpc;
+pub mod policy;
 pub mod server;
 pub mod tickets;
 pub mod tools;
@@ -37,6 +38,7 @@ pub mod transport;
 pub use jsonrpc::{
     JsonRpcError, JsonRpcRequest, JsonRpcResponse, Transport, TransportError, JSONRPC_VERSION,
 };
+pub use policy::ToolPolicyRegistry;
 pub use server::McpServer;
 pub use tickets::{TicketToolError, TicketToolProvider};
 pub use tools::{catalogue, map_tool_call, tool_returns_reply, ToolDef, ToolMapError};

crates/infrastructure/src/orchestrator/mcp/policy.rs

@@ -0,0 +1,76 @@
+//! In-memory MCP tool policy registry.
+
+use std::collections::HashMap;
+use std::sync::RwLock;
+
+use domain::AgentToolPolicy;
+use domain::AgentToolPolicyStore;
+
+/// Stores per-requester MCP tool policies for live assistant sessions.
+#[derive(Default)]
+pub struct ToolPolicyRegistry {
+    policies: RwLock<HashMap<String, AgentToolPolicy>>,
+}
+
+impl ToolPolicyRegistry {
+    /// Builds an empty registry.
+    #[must_use]
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Sets or replaces the policy for `requester`.
+    pub fn set(&self, requester: impl Into<String>, policy: AgentToolPolicy) {
+        self.policies
+            .write()
+            .unwrap()
+            .insert(requester.into(), policy);
+    }
+
+    /// Returns the policy for `requester`, if any.
+    #[must_use]
+    pub fn get(&self, requester: &str) -> Option<AgentToolPolicy> {
+        self.policies.read().unwrap().get(requester).cloned()
+    }
+
+    /// Clears the policy for `requester`.
+    pub fn clear(&self, requester: &str) {
+        self.policies.write().unwrap().remove(requester);
+    }
+}
+
+impl AgentToolPolicyStore for ToolPolicyRegistry {
+    fn set_policy(&self, requester: String, policy: AgentToolPolicy) {
+        self.set(requester, policy);
+    }
+
+    fn get_policy(&self, requester: &str) -> Option<AgentToolPolicy> {
+        self.get(requester)
+    }
+
+    fn clear_policy(&self, requester: &str) {
+        self.clear(requester);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use domain::IssueRef;
+
+    use super::*;
+
+    #[test]
+    fn set_get_clear_roundtrips_by_requester() {
+        let registry = ToolPolicyRegistry::new();
+        let policy = AgentToolPolicy::new(
+            vec!["idea_ticket_read".to_owned()],
+            Some("#7".parse::<IssueRef>().unwrap()),
+            true,
+        );
+        registry.set("assistant-1", policy.clone());
+        assert_eq!(registry.get("assistant-1"), Some(policy));
+        assert_eq!(registry.get("assistant-2"), None);
+        registry.clear("assistant-1");
+        assert_eq!(registry.get("assistant-1"), None);
+    }
+}

crates/infrastructure/src/orchestrator/mcp/server.rs

@@ -16,11 +16,12 @@
 //! at the composition root (M3), exactly like the watcher — no application logic is
 //! duplicated here.
 
+use std::str::FromStr;
 use std::sync::Arc;
 use std::time::Instant;
 
 use application::OrchestratorService;
-use domain::{DomainEvent, OrchestrationSource, Project};
+use domain::{AgentToolPolicy, DomainEvent, IssueRef, OrchestrationSource, Project};
 use serde_json::{json, Value};
 use tokio::sync::mpsc;
 
@@ -28,6 +29,7 @@ use super::jsonrpc::{
     error_codes, JsonRpcError, JsonRpcRequest, JsonRpcResponse, Transport, TransportError,
     JSONRPC_VERSION,
 };
+use super::policy::ToolPolicyRegistry;
 use super::tickets::TicketToolProvider;
 use super::tools::{self, ToolMapError};
 
@@ -65,6 +67,8 @@ pub struct McpServer {
     /// Optional public ticket provider. The MCP surface says `ticket`; the
     /// provider maps those calls to application/domain `Issue` use cases.
     ticket_tools: Option<Arc<dyn TicketToolProvider>>,
+    /// Optional per-requester MCP tool policy registry for constrained sessions.
+    tool_policies: Option<Arc<ToolPolicyRegistry>>,
 }
 
 impl McpServer {
@@ -80,6 +84,7 @@ impl McpServer {
             requester: String::new(),
             ready_sink: None,
             ticket_tools: None,
+            tool_policies: None,
         }
     }
 
@@ -111,6 +116,13 @@ impl McpServer {
         self
     }
 
+    /// Attaches the requester-scoped MCP tool policy registry.
+    #[must_use]
+    pub fn with_tool_policies(mut self, tool_policies: Arc<ToolPolicyRegistry>) -> Self {
+        self.tool_policies = Some(tool_policies);
+        self
+    }
+
     /// Returns a per-connection clone of this server tagged with the connected
     /// peer's `requester` id (the loopback handshake's `requester`, cadrage v5 §1.4).
     ///
@@ -128,6 +140,7 @@ impl McpServer {
             requester: requester.into(),
             ready_sink: self.ready_sink.clone(),
             ticket_tools: self.ticket_tools.clone(),
+            tool_policies: self.tool_policies.clone(),
         }
     }
 
@@ -300,8 +313,17 @@ impl McpServer {
 
     /// The `tools/list` result: the catalogue as MCP tool descriptors.
     fn tools_list_result(&self) -> Value {
+        let policy = self
+            .tool_policies
+            .as_ref()
+            .and_then(|registry| registry.get(&self.requester));
         let tools: Vec<Value> = tools::catalogue()
             .into_iter()
+            .filter(|t| {
+                policy
+                    .as_ref()
+                    .map_or(true, |policy| policy.permits(t.name))
+            })
             .map(|t| {
                 json!({
                     "name": t.name,
@@ -324,6 +346,14 @@ impl McpServer {
             .to_owned();
         let arguments = params.get("arguments").cloned().unwrap_or(json!({}));
 
+        if let Some(policy) = self
+            .tool_policies
+            .as_ref()
+            .and_then(|registry| registry.get(&self.requester))
+        {
+            self.enforce_tool_policy(&policy, &name, &arguments)?;
+        }
+
         // Diagnostics begin beacon (best-effort, jamais le corps task/result) : trace
         // l'entrée d'un `tools/call`, son tool, le peer demandeur et la cible/longueurs.
         let started = Instant::now();
@@ -437,6 +467,47 @@ impl McpServer {
         }
     }
 
+    fn enforce_tool_policy(
+        &self,
+        policy: &AgentToolPolicy,
+        name: &str,
+        arguments: &Value,
+    ) -> Result<(), JsonRpcError> {
+        if !policy.permits(name) {
+            return Err(JsonRpcError::new(
+                error_codes::INVALID_PARAMS,
+                format!(
+                    "tool `{name}` is not permitted for requester {}",
+                    self.requester
+                ),
+            ));
+        }
+        if matches!(name, "idea_ticket_update" | "idea_ticket_update_carnet") {
+            let raw_ref = arguments
+                .get("ref")
+                .and_then(Value::as_str)
+                .ok_or_else(|| {
+                    JsonRpcError::new(
+                        error_codes::INVALID_PARAMS,
+                        format!("tool `{name}` requires a ticket ref under the active policy"),
+                    )
+                })?;
+            let issue_ref = IssueRef::from_str(raw_ref).map_err(|e| {
+                JsonRpcError::new(
+                    error_codes::INVALID_PARAMS,
+                    format!("invalid ticket ref: {e}"),
+                )
+            })?;
+            if !policy.permits_ticket_mutation(name, issue_ref) {
+                return Err(JsonRpcError::new(
+                    error_codes::INVALID_PARAMS,
+                    format!("tool `{name}` is not permitted for ticket {issue_ref}"),
+                ));
+            }
+        }
+        Ok(())
+    }
+
     /// Publishes [`DomainEvent::OrchestratorRequestProcessed`] for a handled
     /// `tools/call`, tagged [`OrchestrationSource::Mcp`]. The requester id is the
     /// connected peer's real agent id (carried in the loopback handshake, cadrage v5