fix(frontend,application): lot utilisateur #315 — détachement Paramètres projet, couleurs projet fiables, restauration conversation custom CLI, images post-aller-retour projet, retrait menus Projects/Project Context (QA verte)

- détachement: le panneau Paramètres du projet devient détachable (mapping historique panel=context → projectSettings dans parseViewWindowParams, DETACHABLE/ViewPanelBody alignés, ProjectsView ne court-circuitant plus le refus); Retry d'échec de détachement préservé
- couleurs projet: projectTheme publie idea:project-theme-changed localement + BroadcastChannel inter-webviews (fenêtres OS détachées), garde de révision par projet dans ProjectsView/ViewWindow contre les lectures settings en course — plus de flash/retour au bleu par défaut
- conversation custom CLI: transcript_restore_expected ne considère plus l'absence de scrollback volatile comme une restauration échouée quand la session rouvre en SessionPlan::None (continuation vide valide); CustomAgentChatView n'affiche plus le faux « conversation liée n'a pas pu être restaurée »
- images: conservation des images de conversation après changement de projet puis retour
- menus Panneaux: retrait des entrées Projects et Project Context (panelOrder WebWorkspace, création/switch via tab-bar +, contexte projet fusionné dans Paramètres du projet)
- QA verte: tests frontend ciblés window/ViewWindow/ProjectSettingsPanel/ProjectsView.detach/projects/CustomAgentChatView/WebDesktopWorkspace + cargo test -p application lifecycle transcript_restore_expected; fichiers .ideai/* (tickets 308-315, index/counter, agents/test, chat-drafts, system-permissions, project-settings.json, attachments/) et scripts/ hors périmètre préservés en worktree; aucun push

frontend/src/app/ViewWindow.tsx

@@ -19,13 +19,18 @@
  * and crucially no `openProject()` — opening a project is the main window's job.
  */
 
-import { useEffect, useMemo, useState } from "react";
+import { useEffect, useMemo, useRef, useState } from "react";
 
 import type { CustomPluginLayoutCell } from "@/domain";
 import type { FocusedProject } from "@/ports";
 import { Panel } from "@/shared";
 import { PANEL_TITLE, type PanelId } from "@/features/projects";
 import { ViewPanelBody, type ViewPanelId } from "@/features/projects";
+import {
+  onProjectThemeChanged,
+  projectThemeStyle,
+  validThemeColor,
+} from "@/features/projects/projectTheme";
 import {
   PluginLayoutCellView,
   PluginRuntimeProvider,
@@ -98,7 +103,8 @@ export function parseViewWindowParams(
     };
   }
 
-  const panel = params.get("panel");
+  const rawPanel = params.get("panel");
+  const panel = rawPanel === "context" ? "projectSettings" : rawPanel;
   if (!panel || !DETACHABLE.has(panel)) return null;
   return { kind: "panel", panel: panel as ViewPanelId };
 }
@@ -108,12 +114,14 @@ export interface ViewWindowProps {
 }
 
 export function ViewWindow({ panel }: ViewWindowProps) {
-  const { focusedProject } = useGateways();
+  const { focusedProject, project } = useGateways();
   // The focused project this window follows. `undefined` = not yet resolved
   // (initial read in flight); `null` = resolved, no project focused.
   const [focus, setFocus] = useState<FocusedProject | null | undefined>(
     undefined,
   );
+  const [themeColors, setThemeColors] = useState<Record<string, string | null>>({});
+  const themeRevisionRef = useRef<Record<string, number>>({});
 
   // Read the current focus at mount, then track changes. Never opens a project:
   // the window is a pure follower of the main window's focus (#47).
@@ -142,8 +150,42 @@ export function ViewWindow({ panel }: ViewWindowProps) {
     };
   }, [focusedProject]);
 
+  useEffect(() => {
+    if (!focus) return;
+    let cancelled = false;
+    const revision = themeRevisionRef.current[focus.id] ?? 0;
+    void project.readProjectSettings(focus.id).then((settings) => {
+      if (
+        !cancelled &&
+        (themeRevisionRef.current[focus.id] ?? 0) === revision
+      ) {
+        setThemeColors((current) => ({
+          ...current,
+          [focus.id]: validThemeColor(settings.themeColor),
+        }));
+      }
+    }).catch(() => {
+      // Keep the last known colour; settings content owns its own retry state.
+    });
+    return () => {
+      cancelled = true;
+    };
+  }, [focus?.id, project]);
+
+  useEffect(() => onProjectThemeChanged(({ projectId, themeColor }) => {
+    themeRevisionRef.current[projectId] =
+      (themeRevisionRef.current[projectId] ?? 0) + 1;
+    setThemeColors((current) => ({
+      ...current,
+      [projectId]: validThemeColor(themeColor),
+    }));
+  }), []);
+
   return (
-    <div className="flex h-full flex-col bg-canvas text-content">
+    <div
+      className="flex h-full flex-col bg-canvas text-content"
+      style={projectThemeStyle(focus ? themeColors[focus.id] : null)}
+    >
       <header className="flex shrink-0 items-center gap-2 border-b border-border px-4 py-2.5">
         <h1 className="text-sm font-semibold text-content">
           {PANEL_TITLE[panel]}