feat(settings): one page per section with a grouped nav and search

Settings moves from a tab bar to /settings/<section>: a left nav grouped
General / Agents / Routing / Git / Projects (a select on narrow screens), a
search box over every section (Ctrl/Cmd+F, Enter opens the first match), and
row primitives. Each AI tool has its page under agents/<id>, the AI Tools
modal becomes the Agents page, Pricing shows every vendor, Git → Worktrees
sets which untracked worktrees the sidebar lists, and each project gets a
page with its own worktree override and Forget all. ?tool= and #ai-tools
links redirect to the path form.

client/src/i18n/locales/en/settings.json

@@ -463,15 +463,6 @@
     "remoteSourceBadgeTitle": "Collected from a remote machine"
   },
   "cursorPathsNote": "Informational: Cursor sessions count here too — Cursor happens to use the same ~/.claude paths as Claude Code (locally and on synced remotes).",
-  "tools": {
-    "label": "Tools",
-    "dashboard": "Dashboard",
-    "claudeCode": "Claude Code",
-    "codex": "Codex",
-    "antigravity": "Antigravity",
-    "aiRouter": "AI Router",
-    "gitCredentials": "Git credentials"
-  },
   "aiRouter": {
     "title": "AI Router",
     "description": "Endpoints that stand in front of Claude Code and Codex — 9Router, OpenRouter, a self-hosted gateway. Save one here, then pick it when you create a workspace.",
@@ -639,5 +630,97 @@
     "save": "Save",
     "close": "Close",
     "saved": "Saved. Backup: {{backup}}"
+  },
+  "settingsNav": {
+    "label": "Settings sections",
+    "back": "Back to Workspace",
+    "group": {
+      "general": "General",
+      "agents": "Agents",
+      "routing": "Routing",
+      "git": "Git",
+      "projects": "Projects"
+    },
+    "section": {
+      "general": {
+        "title": "General",
+        "description": "Workspace housekeeping, data and about."
+      },
+      "appearance": {
+        "title": "Appearance",
+        "description": "Colour mode and theme. Saved in this browser only."
+      },
+      "notifications": {
+        "title": "Notifications",
+        "description": "Browser notifications, alert rules and webhooks."
+      },
+      "agents": {
+        "title": "AI tools",
+        "description": "The AI coding CLIs AgentHub can run: enable, set the default, install and update."
+      },
+      "claudeCode": {
+        "title": "Claude Code",
+        "description": "Claude Code's own configuration, and what AgentHub reads from it."
+      },
+      "codex": {
+        "title": "Codex",
+        "description": "Codex's own configuration, and what AgentHub reads from it."
+      },
+      "tool": {
+        "description": "{{tool}}: path, usage, default model and config files."
+      },
+      "aiRouter": {
+        "title": "AI Router",
+        "description": "Endpoints that stand in front of Claude Code and Codex."
+      },
+      "pricing": {
+        "title": "Pricing",
+        "description": "Model prices for every vendor, used to estimate cost."
+      },
+      "gitCredentials": {
+        "title": "Git credentials",
+        "description": "Logins AgentHub gives git for a dashboard fetch, pull or push."
+      },
+      "worktrees": {
+        "title": "Worktrees",
+        "description": "Which git worktrees the sidebar lists under each project."
+      },
+      "project": {
+        "description": "This project's workspaces and worktree settings."
+      }
+    }
+  },
+  "search": {
+    "placeholder": "Search settings",
+    "noMatch": "No setting matches “{{query}}”."
+  },
+  "worktrees": {
+    "title": "Untracked worktrees",
+    "description": "A worktree with no workspace on it is listed under its project with an Adopt button. Saved in this browser only.",
+    "showUntracked": "Show untracked worktrees",
+    "showUntrackedDesc": "List a repository's worktrees that have no workspace yet.",
+    "claude": "Claude Code worktrees",
+    "claudeDesc": "Worktrees under <repo>/.claude/worktrees/, made by Claude Code's own agents.",
+    "agenthub": "AgentHub-managed worktrees",
+    "agenthubDesc": "Worktrees AgentHub created under its workspaces root."
+  },
+  "project": {
+    "notFound": "No such project.",
+    "facts": "Project",
+    "root": "Root",
+    "mainBranch": "Main branch",
+    "worktreeCount": "Worktrees",
+    "workspaces": "Workspaces",
+    "noWorkspaces": "No workspace in this project yet.",
+    "sources": "Worktree sources",
+    "sourcesDesc": "Override the Worktrees page for this project only.",
+    "override": "Use this project's own setting",
+    "forget": "Forget workspaces",
+    "forgetDesc": "Remove every workspace of this project from AgentHub. Working trees, branches and data on disk are left alone.",
+    "forgetAll": "Forget all workspaces…",
+    "forgetTitle": "Forget {{count}} workspaces?",
+    "forgetBody": "AgentHub drops its record of each one and stops its runs. Nothing on disk is deleted.",
+    "forgetConfirm": "Forget all",
+    "forgetFailed": "Could not forget {{lane}}: {{message}}"
   }
 }