The guide learns the thread it was silent on, and grows a vendor-neutral twin

CLAUDE.md bumps to v14: a new Comments section teaches the comments/ mechanics
(chronology-as-ordering, author vs modified-by, .draft/.trash as the app's,
retract-by-follow-up), and a new "Use the thread: journal your work" section
teaches conduct the guide never had — body is the spec, thread is the journal,
post a plan cold-reader-ready on start, decisions as they're made, questions
as comments, re-read before resuming, close with verification. comments/
leaves the reserved-tracker-keys list; the Layout diagram gains comments/ and
AGENTS.md.

The app now writes a byte-identical twin at AGENTS.md, the vendor-neutral name
most non-Claude tools read — same lifecycle as CLAUDE.md, decided and healed
independently per claimed name, both funneling a markerless foreign file to
the single shared CLAUDE.user.md rescue. AgentGuide.install now returns
[Displacement]; IntegrityRules.claimedRootNames and BoardStore.refreshAgentGuide
cover both names; ChangeNarrator's guide-commit path check widens to both.

DESIGN/08-agent-integration.md amends: the agent-guide section gains the
Comments and Use-the-thread bullets and an AGENTS.md twin paragraph.

Claude-Session: https://claude.ai/code/session_014PtZdPwqZuqEDLc6wZMtEy

KanbanTests/BoardWriterTests.swift

@@ -842,6 +842,23 @@ struct BoardWriterCreateBoardTests {
         #expect(guideText == AgentGuide.content, "the exact shipped guide, not a hand-rolled write")
         #expect(!fixture.exists("MyBoard.kanban/\(AgentGuide.userFilename)"), "nothing existed to rescue at a brand-new root")
     }
+
+    /// **The twin** (ruled 2026-08-09, card dc1314bb): `createBoard` writes `AGENTS.md` alongside
+    /// `CLAUDE.md`, byte-identical — a fresh board never lives even a moment with only one of the two
+    /// claimed guide names.
+    @Test("createBoard installs the AGENTS.md twin too, byte-identical to CLAUDE.md")
+    func createBoardInstallsTheAgentsMdTwin() throws {
+        let fixture = try WriterFixture()
+        defer { fixture.tearDown() }
+        let root = fixture.url("MyBoard.kanban")
+
+        try BoardWriter.createBoard(at: root, title: "My Board")
+
+        let claudeText = try fixture.data("MyBoard.kanban/\(AgentGuide.filename)")
+        let agentsText = try fixture.data("MyBoard.kanban/\(AgentGuide.agentsFilename)")
+        #expect(agentsText == claudeText, "byte-identical, not merely equal-content")
+        #expect(agentsText == Data(AgentGuide.content.utf8))
+    }
 }
 
 // MARK: - Create lane / card