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.

server/lib/router-apply.js

@@ -34,6 +34,7 @@ const path = require("node:path");
 
 const routers = require("./ai-routers");
 const { patchSettings } = require("./cc-mutate");
+const { excludeFromGit } = require("./git-exclude");
 const { getCodexHome } = require("./codex-home");
 const { lanesByRouter, setRouterProfile } = require("./lanes");
 
@@ -72,26 +73,6 @@ function readOrNull(name) {
   }
 }
 
-/**
- * The lane's own git directory. For a normal clone that is `<cwd>/.git`; for a
- * LINKED WORKTREE — which is what every managed lane is — `.git` is a pointer
- * FILE, and joining `info/exclude` onto it names a path that cannot exist.
- *
- * @returns {string|null} absolute git dir, or null when this is not a repo
- */
-function gitDirOf(laneDir) {
-  const dotGit = path.join(laneDir, ".git");
-  let stat;
-  try {
-    stat = fs.statSync(dotGit);
-  } catch {
-    return null; // not a git repo — a perfectly normal adopted directory
-  }
-  if (stat.isDirectory()) return dotGit;
-  const match = fs.readFileSync(dotGit, "utf8").match(/^gitdir:\s*(.+)$/m);
-  return match ? path.resolve(laneDir, match[1].trim()) : null;
-}
-
 /**
  * Idempotently keep `.claude/settings.local.json` out of git, for two reasons
  * that both matter:
@@ -101,28 +82,12 @@ function gitDirOf(laneDir) {
  *    is deleted and the lane silently loses its router.
  *  - The file holds an API key. Untracked means `git add -A` can commit it.
  *
- * Best effort: a lane that is not a repo, or a git dir that cannot be written,
- * must not fail an otherwise-successful attach.
+ * The backup directory beside it, for the same reason plus one more: those
+ * copies hold the API key too, and they are what a user sees as a dozen
+ * untracked files appearing in their project while they switch routers.
  */
 function excludeSettingsFromGit(laneDir) {
-  // The backup directory beside it, for the same reason plus one more: those
-  // copies hold the API key too, and they are what a user sees as a dozen
-  // untracked files appearing in their project while they switch routers.
-  const lines = [".claude/settings.local.json", ".claude/.cc-config-backups/"];
-  try {
-    const gitDir = gitDirOf(laneDir);
-    if (!gitDir) return;
-    const excludePath = path.join(gitDir, "info", "exclude");
-    fs.mkdirSync(path.dirname(excludePath), { recursive: true });
-    let existing = fs.existsSync(excludePath) ? fs.readFileSync(excludePath, "utf8") : "";
-    const present = new Set(existing.split("\n"));
-    const missing = lines.filter((line) => !present.has(line));
-    if (missing.length === 0) return;
-    if (existing && !existing.endsWith("\n")) existing += "\n";
-    fs.writeFileSync(excludePath, `${existing}${missing.join("\n")}\n`);
-  } catch {
-    /* best effort — see above */
-  }
+  excludeFromGit(laneDir, [".claude/settings.local.json", ".claude/.cc-config-backups/"]);
 }
 
 /**