feat: per-change-block hunk actions (#50), codex lanes without a pipeline, macOS LaunchAgent

- git (#50): stage-hunk/discard-hunk take an optional `block` — one run of
  consecutive +/- lines inside an @@ hunk. `onlyBlock` (server/lib/git-diff.js)
  cuts git's fresh hunk down to it, folding the other blocks into the side
  being checked; LaneDiffView hangs one review bar per block (unified + split)
  and its arrows walk blocks.
- git exclude: entries AgentHub writes for a lane go to the COMMON git dir with
  the lane's path prefix (server/lib/git-exclude.js, used by router-apply and
  lane-mcp) — a linked worktree's own info/exclude is never read by git, and a
  subdir lane has no .git. MCP sync no longer fails with ENOTDIR on a worktree
  lane or creates a stray .git in a non-repo lane.
- codex lanes carry no pipeline: codex-ingest mirrors only idle/running,
  codex-nudge is removed, agents install writes nothing for codex, the
  Workspace hides stage/pipeline/feature pickers/PipelineMap for them, and
  every server start clears leftover codex stage data and the old AGENTS.md
  stage block.
- Changes panel: a whole file opens for reading and enters the editor on a
  click on its text (caret at the clicked line), not automatically.
- macOS: LaunchAgent start-at-login (scripts/launchd-service.js, picked by
  scripts/service-manager.js).
- Adds the AgentHub introduction slides and their image-embedding script.

client/src/components/lanes/__tests__/LaneDiffView.test.tsx

@@ -422,8 +422,8 @@ describe("LaneDiffView — hunk review bar navigation", () => {
     Object.defineProperty(scroller, "scrollHeight", { value: 1000 });
     Object.defineProperty(scroller, "clientHeight", { value: 100 });
     scroller.getBoundingClientRect = () => ({ top: 0 }) as DOMRect;
-    for (const el of view.container.querySelectorAll<HTMLElement>("[data-hunk-index]")) {
-      const k = Number(el.dataset.hunkIndex);
+    for (const el of view.container.querySelectorAll<HTMLElement>("[data-change-index]")) {
+      const k = Number(el.dataset.changeIndex);
       el.getBoundingClientRect = () => ({ top: k * 100 - scroller.scrollTop }) as DOMRect;
     }
     return scroller;
@@ -454,6 +454,49 @@ describe("LaneDiffView — hunk review bar navigation", () => {
     expect(screen.getAllByRole("button", { name: "Next change" })[2]).toBeDisabled();
   });
 
+  it("hangs one bar under EACH +/- block of a single hunk, in both layouts (#50)", () => {
+    const merged: LaneChangeFile = {
+      ...FILE,
+      hunks: [
+        {
+          header: "@@ -1,6 +1,6 @@",
+          context: "",
+          oldStart: 1,
+          newStart: 1,
+          lines: [
+            { type: "del" as const, oldLine: 1, newLine: null, text: "a" },
+            { type: "add" as const, oldLine: null, newLine: 1, text: "A" },
+            { type: "ctx" as const, oldLine: 2, newLine: 2, text: "b" },
+            { type: "del" as const, oldLine: 3, newLine: null, text: "c" },
+            { type: "ctx" as const, oldLine: 4, newLine: 3, text: "d" },
+            { type: "add" as const, oldLine: null, newLine: 4, text: "E" },
+            { type: "ctx" as const, oldLine: 5, newLine: 5, text: "f" },
+          ],
+        },
+      ],
+    };
+    const seen: number[] = [];
+    for (const layout of ["unified", "split"] as const) {
+      const { unmount } = render(
+        <LaneDiffView
+          file={merged}
+          layout={layout}
+          hunkActions={(c) => {
+            seen.push(c.block);
+            return <span />;
+          }}
+        />
+      );
+      expect(screen.getAllByTestId("lane-hunk-bar").map((b) => b.textContent)).toEqual([
+        expect.stringContaining("1 of 3"),
+        expect.stringContaining("2 of 3"),
+        expect.stringContaining("3 of 3"),
+      ]);
+      unmount();
+    }
+    expect(seen).toEqual([0, 1, 2, 0, 1, 2]);
+  });
+
   it("leaves an unwindowed review diff uncapped, so the panel is its only scroller", () => {
     render(<LaneDiffView file={three} layout="unified" />);
     expect(screen.getByTestId("lane-diff-view").className).not.toContain("max-h-[60vh]");