fix(panes): /tui works in panes with workspace instructions

Claude refused `/tui` ("Cannot switch renderers in this session — it has
restrictions a restart can't carry over") in every pane started with
--append-system-prompt-file, i.e. any workspace with instructions (member
panes usually have the owner's). The instructions are now written as the only
CLAUDE.md of a folder of their own (<data dir>/workspace-prompts/<id>/, a
member's prompt-<id>/ in the handoff dir via write-as), passed as one more
--add-dir with CLAUDE_CODE_ADDITIONAL_DIRECTORIES_CLAUDE_MD=1. Verified with
Claude Code 2.1.301: the file is listed in /memory and /tui switches. Codex
is unchanged (its pointer line names the same file).

server/lib/lane-sources.js

@@ -7,7 +7,7 @@
  * workspace's own folder and not be or contain the OS home; an uploaded file
  * is stored by AgentHub under `<data dir>/workspace-context/<laneId>/` with a
  * name it chooses, so a request never names a path on disk. Only Claude
- * (`--add-dir`, `--append-system-prompt-file=`) and Codex (`--add-dir`,
+ * (`--add-dir`, the instructions as a CLAUDE.md in a folder of their own) and Codex (`--add-dir`,
  * `-c developer_instructions=`) can take them; every other tool is reported
  * unsupported and its panes get nothing. The workspace OWNER's own agent
  * instructions (`user_prefs.instructions`, Settings → My agent instructions)
@@ -184,7 +184,9 @@ function removeSource(laneId, sourceId) {
 function removeLaneContext(laneId) {
   const dir = contextDir(laneId);
   if (ownsFile(dir)) fs.rmSync(dir, { recursive: true, force: true });
-  fs.rmSync(path.join(getDataDir(), "workspace-prompts", `${Number(laneId)}.md`), { force: true });
+  const prompts = path.join(getDataDir(), "workspace-prompts");
+  fs.rmSync(path.join(prompts, String(Number(laneId))), { recursive: true, force: true });
+  fs.rmSync(path.join(prompts, `${Number(laneId)}.md`), { force: true }); // before v2.8.9
 }
 
 /** Instructions text as stored: a string of at most MAX_INSTRUCTIONS, blank ⇒ null. */
@@ -286,18 +288,23 @@ function launchExtras(laneId, tool) {
   // A data dir that cannot be written costs the pane its instructions (all of
   // Claude's, Codex's past the inline budget), never its start — same as a
   // vanished source.
+  // The file is a `CLAUDE.md` alone in a folder of its own: Claude reads it as
+  // memory from that folder (`--add-dir` + CLAUDE_CODE_ADDITIONAL_DIRECTORIES_
+  // CLAUDE_MD, pty-run.js), not as `--append-system-prompt-file` — a custom
+  // system prompt is a launch flag Claude cannot carry over a restart, so it
+  // refused `/tui` (switching renderer restarts the session) in every pane
+  // that had instructions. Codex names the same file in its pointer line.
   try {
+    const sub = `prompt-${Number(laneId)}`;
     if (member) {
-      const file = require("./run-as").handoffWrite(
-        member,
-        `prompt-${Number(laneId)}.md`,
-        systemPrompt
-      );
+      const runAs = require("./run-as");
+      runAs.mkdirAs(member, path.join(runAs.handoffDir(member), sub));
+      const file = runAs.handoffWrite(member, path.join(sub, "CLAUDE.md"), systemPrompt);
       return { addDirs, systemPrompt, systemPromptFile: file };
     }
-    const dir = path.join(getDataDir(), "workspace-prompts");
+    const dir = path.join(getDataDir(), "workspace-prompts", String(Number(laneId)));
     fs.mkdirSync(dir, { recursive: true, mode: 0o700 });
-    const systemPromptFile = path.join(dir, `${Number(laneId)}.md`);
+    const systemPromptFile = path.join(dir, "CLAUDE.md");
     fs.writeFileSync(systemPromptFile, systemPrompt, { mode: 0o600 });
     return { addDirs, systemPrompt, systemPromptFile };
   } catch (err) {