Add Grok orchestration group routing (#8058)

* docs: design Grok orchestration group

* docs: plan Grok orchestration group implementation

* fix: add Grok orchestration group

* test(orchestration): accept Windows skill newlines

* Fix @grok orchestration group matching and remove stale planning docs

- Reuse the shared buildAgentNameRe matcher in groups.ts instead of a
  divergent local regex, so orchestration groups honor the same
  Windows launcher-suffix rule (grok.exe/.cmd/.bat/.ps1) as the rest
  of Orca's agent-title detection.
- Add test coverage for real Grok OSC title shapes (spinner-collapsed,
  session titles) and Windows launcher-suffix titles.
- Delete the now-completed design and implementation-plan docs for
  the Grok orchestration group work.

---------

Co-authored-by: Jinjing <6427696+AmethystLiang@users.noreply.github.com>

config/scripts/orchestration-skill-guidance.test.mjs

@@ -11,7 +11,9 @@ function readSkill() {
 
 function getSection(markdown, heading) {
   const escapedHeading = heading.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
-  const match = markdown.match(new RegExp(`## ${escapedHeading}\\n([\\s\\S]*?)(?=\\n## |$)`))
+  const match = markdown.match(
+    new RegExp(`## ${escapedHeading}\\r?\\n([\\s\\S]*?)(?=\\r?\\n## |$)`)
+  )
 
   expect(match).not.toBeNull()
 
@@ -189,6 +191,13 @@ describe('orchestration skill guidance', () => {
     expect(skill).not.toContain('every 2 minutes')
   })
 
+  it('documents @grok in the Messaging group address list', () => {
+    const skill = readSkill()
+    const messaging = getSection(skill, 'Messaging')
+
+    expect(messaging).toContain('`@grok`')
+  })
+
   it('keeps agent-first launch, handle recovery, and inbox injection distinct', () => {
     const skill = readSkill()
     const messaging = getSection(skill, 'Messaging')