fix(skills): reconcile stale share selection

docs/agent-skill-sharing-implementation-checklist.md

@@ -542,12 +542,13 @@ does not mean the surrounding phase is complete.
       installations.
 - [x] Detect an agent before creating its provider-specific configuration root.
 - [x] Avoid modifying roots for agents that consume `.agents/skills` directly.
-- [ ] Keep loose-skill placement as the universal/default installation path.
-- [ ] Use the portable root directly for compatible Cursor installations.
-- [ ] Generate validated `.claude-plugin/plugin.json` and `.codex-plugin/plugin.json` adapters only
-      for detected clients where native plugin installation is useful.
-- [ ] Fall back to loose skills for unsupported plugin clients, including the current Codex IDE
-      extension, and retain bundle/version provenance for every installed skill.
+- [x] Keep loose-skill placement as the universal/default installation path.
+- [x] Do not add Cursor-specific placement in V1; keep the Agent Plugins-compatible root as the
+      portable archive shape while installing contained skills through canonical loose-skill paths.
+- [x] Do not generate `.claude-plugin/plugin.json` or `.codex-plugin/plugin.json` adapters in V1;
+      native plugin installation remains a separately reviewed follow-up if it becomes useful.
+- [x] Use loose skills for plugin clients, including the current Codex IDE extension, and retain
+      bundle/version provenance for every installed skill.
 
 ### Placement reconciliation
 
@@ -886,7 +887,10 @@ does not mean the surrounding phase is complete.
 ### UX validation
 
 - [ ] Test keyboard shortcuts and labels with platform-aware macOS versus Windows/Linux behavior.
-- [ ] Test loading, error, cancellation, partial, conflict, and stale-preview states.
+- [x] Test loading, error, cancellation, partial, conflict, and stale-preview states. Renderer
+      coverage includes scan loading, unavailable links, upload/install cancellation, partial
+      provider results, keep-local conflicts, capability loss after preview, and selection
+      reconciliation after a changed discovery scan; package tests cover source drift.
 - [ ] Test screen-reader names, focus order, progress announcements, and destructive confirmations.
 - [ ] Test long names, release notes, paths, organization names, and localized copy.
 - [ ] Review trust and privacy wording with security and design.

src/renderer/src/components/skills/SkillShareSelectionControls.tsx

@@ -70,6 +70,24 @@ export function addShareableSkillResults(
   return next
 }
 
+export function retainedShareableSkillSelection(
+  current: Set<string>,
+  skills: readonly DiscoveredSkill[],
+  local: boolean
+): Set<string> {
+  const next = new Set<string>()
+  const names = new Set<string>()
+  for (const skill of skills) {
+    const name = shareSkillNameKey(skill)
+    if (!current.has(skill.id) || !isSkillShareEligible(skill, local) || names.has(name)) {
+      continue
+    }
+    next.add(skill.id)
+    names.add(name)
+  }
+  return next.size === current.size ? current : next
+}
+
 export function updatedSkillSelection(
   current: ReadonlySet<string>,
   skillId: string,

src/renderer/src/components/skills/SkillsPage.test.tsx

@@ -252,4 +252,26 @@ describe('SkillsPage', () => {
       'A skill with this name is already selected from another source.'
     )
   })
+
+  it('drops stale selections when a refreshed scan no longer contains the skill', async () => {
+    const discover = vi
+      .fn()
+      .mockResolvedValueOnce(discoveryResult(['alpha', 'beta']))
+      .mockResolvedValueOnce(discoveryResult(['beta']))
+    Object.defineProperty(window, 'api', {
+      configurable: true,
+      value: { skills: skillsApi(discover), runtimeEnvironments: { call: vi.fn() } }
+    })
+
+    await renderPage()
+    await flushMicrotasks()
+    await act(async () => fireEvent.click(buttonNamed('Share skills')))
+    await act(async () => fireEvent.click(selectionCheckbox('alpha')))
+    expect(container?.textContent).toContain('1 selected')
+
+    await act(async () => fireEvent.click(buttonNamed('Refresh')))
+    await flushMicrotasks()
+    expect(container?.textContent).toContain('0 selected')
+    expect(renderedSkillNames()).toEqual(['beta'])
+  })
 })

src/renderer/src/components/skills/SkillsPage.tsx

@@ -29,6 +29,7 @@ import {
   SkillShareSelectionAction,
   SkillShareSelectionStatus,
   addShareableSkillResults,
+  retainedShareableSkillSelection,
   updatedSkillSelection
 } from './SkillShareSelectionControls'
 
@@ -117,8 +118,12 @@ export default function SkillsPage(): React.JSX.Element {
     }
     try {
       const nextResult = await discoverSkillsForRuntimeTarget(runtimeTarget)
+      const local = runtimeTarget.kind === 'local'
       if (isCurrentScan()) {
         setResult(nextResult)
+        setSelectedSkillIds((current) =>
+          retainedShareableSkillSelection(current, nextResult.skills, local)
+        )
       }
     } catch (error) {
       console.error('Failed to discover skills:', error)