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.

scripts/plugin-doctor.js

@@ -233,16 +233,17 @@ function skillPluginStatus() {
  * about.
  */
 function systemdStatus() {
-  const svc = require("./systemd-service");
+  const svc = require("./service-manager");
   const unit = svc.unitPath("agenthub");
+  const row = svc.kind;
 
   if (!svc.unitIsOurs("agenthub")) {
     if (fs.existsSync(unit)) {
-      return ["warn", "systemd", `${unit} exists but was not written by AgentHub — left untouched`];
+      return ["warn", row, `${unit} exists but was not written by AgentHub — left untouched`];
     }
     return [
       "ok",
-      "systemd",
+      row,
       svc.systemctlAvailable()
         ? "no unit — the server is started per session (install one with `agenthub service install`)"
         : "not available on this platform — the server is started per session",
@@ -252,7 +253,7 @@ function systemdStatus() {
   if (svc.unitIsStale("agenthub", PLUGIN_ROOT)) {
     return [
       "warn",
-      "systemd",
+      row,
       `${unit} still points at a previous plugin version — the dashboard will NOT come back after a reboot. ` +
         `Starting a new Claude Code session repairs it; or run: node ${path.join(PLUGIN_ROOT, "scripts", "plugin-bootstrap.js")} --force`,
     ];
@@ -261,11 +262,13 @@ function systemdStatus() {
   if (!svc.unitIsActive("agenthub")) {
     return [
       "warn",
-      "systemd",
-      "unit is installed and current but not running — start it with `systemctl --user start agenthub`",
+      row,
+      svc.kind === "launchd"
+        ? "LaunchAgent is installed and current but not running — start it with `agenthub service install`"
+        : "unit is installed and current but not running — start it with `systemctl --user start agenthub`",
     ];
   }
-  return ["ok", "systemd", "unit is current and running — the dashboard survives reboots"];
+  return ["ok", row, `${svc.label} is current and running — the dashboard survives reboots`];
 }
 
 /**