feat: add workspace agents for reusable agent definitions across patterns

Introduce a workspace-level agent library that allows users to define
agents once and reference them from multiple orchestration patterns.

Domain model:
- Add WorkspaceAgentDefinition type with name, model, instructions, etc.
- Extend PatternAgentDefinition with optional workspaceAgentId and overrides
- Add resolution helpers that merge workspace agent base with per-pattern overrides
- Extend WorkspaceSettings with agents array and normalize on load

IPC & main process:
- Add saveWorkspaceAgent/deleteWorkspaceAgent IPC channels and handlers
- Resolve workspace agent references in buildEffectivePattern before
  sending to sidecar (no C# changes needed)

Settings UI:
- Add 'Agents' tab under Orchestration in the Settings panel
- Create WorkspaceAgentEditor component using ToolingEditorShell
- Show usage count (which patterns reference each agent)

Pattern editor integration:
- Add agent picker dropdown: 'New inline agent' or 'From library'
- Show linked badge (chain icon) on referenced agent graph nodes
- Show linked workspace agent banner in the inspector
- Add 'Save to Agent Library' action to promote inline agents
- Add 'Unlink' action to convert referenced agents back to inline

Tests:
- Add unit tests for resolution helpers (resolvePatternAgent,
  resolvePatternAgents, findWorkspaceAgentUsages, normalize)
- Update existing tooling test for new agents field

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/AryxAppService.ts

@@ -36,6 +36,11 @@ import {
   type ReasoningEffort,
   validatePatternDefinition,
 } from '@shared/domain/pattern';
+import {
+  normalizeWorkspaceAgentDefinition,
+  resolvePatternAgents,
+  type WorkspaceAgentDefinition,
+} from '@shared/domain/workspaceAgent';
 import {
   applyDiscoveredMcpServerStatus,
   listAcceptedDiscoveredMcpServers,
@@ -813,6 +818,39 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     return this.persistAndBroadcast(workspace);
   }
 
+  async saveWorkspaceAgent(agent: WorkspaceAgentDefinition): Promise<WorkspaceState> {
+    const workspace = await this.loadWorkspace();
+    const agents = workspace.settings.agents ?? [];
+    const existingIndex = agents.findIndex((current) => current.id === agent.id);
+    const timestamp = nowIso();
+    const candidate = normalizeWorkspaceAgentDefinition({
+      ...agent,
+      createdAt: existingIndex >= 0 ? agents[existingIndex].createdAt : timestamp,
+      updatedAt: timestamp,
+    });
+
+    if (!candidate.name) {
+      throw new Error('Workspace agent name is required.');
+    }
+
+    if (existingIndex >= 0) {
+      agents[existingIndex] = candidate;
+    } else {
+      agents.push(candidate);
+    }
+
+    workspace.settings.agents = agents;
+    return this.persistAndBroadcast(workspace);
+  }
+
+  async deleteWorkspaceAgent(agentId: string): Promise<WorkspaceState> {
+    const workspace = await this.loadWorkspace();
+    workspace.settings.agents = (workspace.settings.agents ?? []).filter(
+      (agent) => agent.id !== agentId,
+    );
+    return this.persistAndBroadcast(workspace);
+  }
+
   async createSession(projectId: string, patternId: string): Promise<WorkspaceState> {
     const workspace = await this.loadWorkspace();
     const project = this.requireProject(workspace, projectId);
@@ -955,7 +993,7 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     const project = this.requireProject(workspace, session.projectId);
     const pattern = this.requirePattern(workspace, session.patternId);
     const effectivePattern = this.applyProjectCustomizationToPattern(
-      await this.buildEffectivePattern(pattern, session),
+      await this.buildEffectivePattern(pattern, session, workspace.settings.agents ?? []),
       project,
     );
     const projectInstructions = resolveProjectInstructionsContent(project.customization);
@@ -1014,7 +1052,7 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     const project = this.requireProject(workspace, session.projectId);
     const pattern = this.requirePattern(workspace, session.patternId);
     const effectivePattern = this.applyProjectCustomizationToPattern(
-      await this.buildEffectivePattern(pattern, session),
+      await this.buildEffectivePattern(pattern, session, workspace.settings.agents ?? []),
       project,
     );
     const projectInstructions = resolveProjectInstructionsContent(project.customization);
@@ -1068,7 +1106,7 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     const project = this.requireProject(workspace, session.projectId);
     const pattern = this.requirePattern(workspace, session.patternId);
     const effectivePattern = this.applyProjectCustomizationToPattern(
-      await this.buildEffectivePattern(pattern, session),
+      await this.buildEffectivePattern(pattern, session, workspace.settings.agents ?? []),
       project,
     );
     const projectInstructions = resolveProjectInstructionsContent(project.customization);
@@ -2919,10 +2957,12 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
   private async buildEffectivePattern(
     pattern: PatternDefinition,
     session: SessionRecord,
+    workspaceAgents: ReadonlyArray<WorkspaceAgentDefinition>,
   ): Promise<PatternDefinition> {
+    const resolvedPattern = resolvePatternAgents(pattern, workspaceAgents);
     const patternWithSessionConfig = session.sessionModelConfig
-      ? applySessionModelConfig(pattern, session)
-      : pattern;
+      ? applySessionModelConfig(resolvedPattern, session)
+      : resolvedPattern;
     const patternWithApprovalSettings = applySessionApprovalSettings(patternWithSessionConfig, session);
 
     const modelCatalog = await this.loadAvailableModelCatalog();

src/main/ipc/registerIpcHandlers.ts

@@ -34,6 +34,7 @@ import type {
   SaveLspProfileInput,
   SaveMcpServerInput,
   SavePatternInput,
+  SaveWorkspaceAgentInput,
   SendSessionMessageInput,
   SetPatternFavoriteInput,
   SetProjectAgentProfileEnabledInput,
@@ -148,6 +149,12 @@ export function registerIpcHandlers(
   ipcMain.handle(ipcChannels.deleteLspProfile, (_event, profileId: string) =>
     service.deleteLspProfile(profileId),
   );
+  ipcMain.handle(ipcChannels.saveWorkspaceAgent, (_event, input: SaveWorkspaceAgentInput) =>
+    service.saveWorkspaceAgent(input.agent),
+  );
+  ipcMain.handle(ipcChannels.deleteWorkspaceAgent, (_event, agentId: string) =>
+    service.deleteWorkspaceAgent(agentId),
+  );
   ipcMain.handle(ipcChannels.describeTerminal, () => service.describeTerminal());
   ipcMain.handle(ipcChannels.createTerminal, () => service.createTerminal());
   ipcMain.handle(ipcChannels.restartTerminal, () => service.restartTerminal());