refactor: remove pattern domain and migrate renderer to workflow-only

- Delete src/shared/domain/pattern.ts and all pattern-specific renderer
  components (PatternEditor, NewSessionModal, pattern-graph directory,
  patternGraph lib) and their tests
- Migrate all renderer imports from @shared/domain/pattern to
  @shared/domain/workflow (ReasoningEffort, reasoningEffortOptions,
  WorkflowOrchestrationMode, AgentNodeConfig, WorkflowDefinition)
- Update App.tsx: remove workflowToPattern bridge, createDraftPattern,
  NewSessionModal; sessions now created directly with default workflow
- Update ChatPane, ActivityPanel, Sidebar to accept WorkflowDefinition
  instead of PatternDefinition and derive agents/mode from workflow
- Update SettingsPanel: remove PatternsSection nav item, pattern editing
  state, and pattern-related props; update text references
- Update RunTimeline and modeAccent/modeVisuals records to use
  WorkflowOrchestrationMode (drop magentic mode entry)
- Update sessionActivity.ts to use generic agent interface

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

src/renderer/components/AgentConfigFields.tsx

@@ -8,7 +8,7 @@ import {
   providerMeta,
   type ModelDefinition,
 } from '@shared/domain/models';
-import { reasoningEffortOptions, type ReasoningEffort } from '@shared/domain/pattern';
+import { reasoningEffortOptions, type ReasoningEffort } from '@shared/domain/workflow';
 
 import { ProviderIcon } from './ProviderIcons';