feat: layer runtime and model selection across conversation, project and global

- Store runtime selection as { provider?, model? } layers and resolve them per
  field (conversation -> project -> global); drop the legacy auto provider.
- Migrate stored selections (database v49) and clear deleted profile ids.
- Re-resolve selections in Main per request and at queue dispatch.
- Add ProjectRuntimeSelector and a two-column RuntimeModelPicker; manage
  link opens model connections; restore per-runtime default model tabs.
- Stop duplicating trusted instructions and history across OpenCode,
  Continue and DeepSeek Harness runtimes.
- Document the layered design, global provider removal plan and planned
  purpose-specific models.

src/main/remote-agent/managed-remote-execution-services.ts

@@ -1,7 +1,10 @@
 import { join } from 'node:path'
 import { SqliteRuntimeSessionBindingStore } from '../agent/runtime-session-binding-store'
 import type { ResolvedModelProfile } from '../runtime-settings-store'
-import type { AgentRuntimeSelection } from '../../shared/runtime-selection-contracts'
+import type {
+  AgentRuntimeSelection,
+  RuntimeSelectionLayer
+} from '../../shared/runtime-selection-contracts'
 import type { SshHostStore } from '../ssh/ssh-host-store'
 import {
   resolveBundledRemoteRuntimeResourcePaths,
@@ -44,7 +47,7 @@ export type ManagedRemoteExecutionServicesOptions = {
     selection: AgentRuntimeSelection
   ): Promise<ResolvedModelProfile | undefined>
   resolveRuntimeSelection(
-    selection: AgentRuntimeSelection
+    layer: RuntimeSelectionLayer | undefined
   ): Promise<AgentRuntimeSelection>
 }
 

src/main/remote-agent/remote-project-save-service.test.ts

@@ -1,7 +1,10 @@
 import { EventEmitter } from 'node:events'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import type { AssistantProject } from '../../shared/assistant-contracts'
-import type { AgentRuntimeSelection } from '../../shared/runtime-selection-contracts'
+import type {
+  AgentRuntimeSelection,
+  RuntimeSelectionLayer
+} from '../../shared/runtime-selection-contracts'
 import type { SshConnectionTarget } from '../ssh/ssh-host-store'
 import { verifyAgentInstallationId } from '../ssh/ssh-agent-command'
 import type { AgentInstallationIdentity } from './agent-installation-manager'
@@ -110,7 +113,7 @@ type HarnessOptions = {
   create?: () => AssistantProject
   update?: () => AssistantProject
   resolveRuntimeSelection?: (
-    selection: AgentRuntimeSelection
+    layer: RuntimeSelectionLayer | undefined
   ) => Promise<AgentRuntimeSelection>
 }
 
@@ -262,7 +265,7 @@ function harness(options: HarnessOptions = {}) {
     },
     resolveRuntimeSelection:
       options.resolveRuntimeSelection ??
-      (async (selection) => selection),
+      (async (layer) => ({ provider: layer?.provider === 'continue' ? 'continue' : 'opencode' }) as AgentRuntimeSelection),
     runtimeValidator: {
       validate: vi.fn(async () => {
         calls.push('runtime')

src/main/remote-agent/remote-project-save-service.ts

@@ -11,7 +11,10 @@ import {
   remoteWorkspaceValidateResultSchema,
   type RemoteWorkspaceHandle
 } from '../../shared/remote-agent-contracts'
-import type { AgentRuntimeSelection } from '../../shared/runtime-selection-contracts'
+import type {
+  AgentRuntimeSelection,
+  RuntimeSelectionLayer
+} from '../../shared/runtime-selection-contracts'
 import type {
   AssistantDatabase,
   SshProjectWrite
@@ -99,11 +102,11 @@ type ActiveSave = {
 type RemoteProjectPreparationDraft = Readonly<{
   hostId: string
   remoteRootPath: string
-  runtimeSelection: AgentRuntimeSelection
+  runtimeSelection?: RuntimeSelectionLayer
 }>
 
 type PreparedRemoteProject = Readonly<{
-  runtimeSelection: AgentRuntimeSelection
+  runtimeSelection?: RuntimeSelectionLayer
   target: SshConnectionTarget
   installation: AgentInstallationIdentity
   connection: RemoteAgentConnection
@@ -125,7 +128,7 @@ export type RemoteProjectSaveServiceOptions = {
   installationManager: Pick<AgentInstallationManager, 'activateInstalled'>
   connectionManager: Pick<RemoteAgentConnectionManager, 'acquire'>
   resolveRuntimeSelection(
-    selection: AgentRuntimeSelection
+    layer: RuntimeSelectionLayer | undefined
   ): Promise<AgentRuntimeSelection>
   runtimeValidator?: RemoteProjectRuntimeValidator
   notify?: (