feat(ui): a Claude-Desktop-style home for every workspace

/workspace?lane=<id> opens on the workspace's home (WorkspaceHome): a prompt
box whose Start opens a new session in the first free pane slot, Recents (a
live session attaches its pane, any other opens its transcript, nothing
resumes), and Instructions / Memory / Context / Folder. Instructions live in
lanes.instructions, extra folders and uploaded files in the new lane_sources
table (copies under <data dir>/workspace-context/<lane id>/); spawnRun reads
them from the lane's rows and hands Claude --add-dir + an appended system
prompt file, Codex --add-dir + developer_instructions. Memory is read-only.

Every dashboard pane carries AGENTHUB_RUN_ID; hooks forward it and the run
records which session the pane holds (a Claude pane follows /clear and
/resume but not a nested claude -p), so the sidebar and notifications open
the right pane (&run=). Settings loses its Projects group; Worktrees now
decides which worktrees Add folder suggests.

server/lib/pty-run.js

@@ -91,9 +91,34 @@ function makeErr(code, message) {
  * interactive afterward (unlike `-p`, which forces print-and-exit and closes
  * stdin).
  */
-function buildClaudeArgv({ model, permissionMode, effort, resumeSessionId, initialPrompt }) {
+/**
+ * A prompt as an argv element no CLI can read as an option: one that starts
+ * with "-" (`-c fix it`) would otherwise be parsed as flags — `claude -c`
+ * continues the last conversation, `-p` turns the pane into print mode. A
+ * leading space keeps it a positional and changes nothing the model reads.
+ */
+function promptArg(p) {
+  return p.startsWith("-") ? ` ${p}` : p;
+}
+
+function buildClaudeArgv({
+  model,
+  permissionMode,
+  effort,
+  resumeSessionId,
+  initialPrompt,
+  addDirs = [],
+  systemPromptFile = null,
+}) {
   const argv = ["claude"];
+  // `--add-dir` is VARIADIC (`<directories...>`): it swallows every following
+  // argument up to the next option, so it goes first, where `--permission-mode`
+  // always ends it — after the prompt it would eat the prompt as a directory.
+  if (addDirs.length) argv.push("--add-dir", ...addDirs);
   argv.push("--permission-mode", permissionMode || "auto");
+  // From a file: the instructions can be long, and the whole argv has to fit
+  // in one tmux message. `=` form, so the path is never read as an option.
+  if (systemPromptFile) argv.push(`--append-system-prompt-file=${systemPromptFile}`);
   // Puts "bypass permissions" INTO the pane's shift+tab cycle without turning
   // it on: `claude --help` — "Enable bypassing all permission checks as an
   // option, without it being enabled by default." Without it the cycle is only
@@ -104,7 +129,7 @@ function buildClaudeArgv({ model, permissionMode, effort, resumeSessionId, initi
   if (model) argv.push("--model", model);
   if (effort && EFFORT_LEVELS.has(effort)) argv.push("--effort", effort);
   if (resumeSessionId) argv.push("--resume", resumeSessionId);
-  if (initialPrompt) argv.push(initialPrompt);
+  if (initialPrompt) argv.push(promptArg(initialPrompt));
   return argv;
 }
 
@@ -124,6 +149,9 @@ function buildCodexArgv({
   bypass,
   initialPrompt,
   routerProfile,
+  addDirs = [],
+  systemPrompt = null,
+  systemPromptFile = null,
 }) {
   const argv = ["codex"];
   // Before the subcommand and before the prompt: `-p` layers
@@ -141,7 +169,15 @@ function buildCodexArgv({
     if (approval) argv.push("-a", approval);
   }
   if (effort && CODEX_EFFORTS.has(effort)) argv.push("-c", `model_reasoning_effort=${effort}`);
-  if (initialPrompt) argv.push(initialPrompt);
+  for (const dir of addDirs) argv.push("--add-dir", dir);
+  // `-c` parses its value as TOML; a JSON string literal is a valid TOML basic
+  // string, so any text — quotes, newlines — arrives as one string.
+  if (systemPrompt) {
+    const { codexInstructions, tomlString } = require("./lane-sources");
+    const text = codexInstructions(systemPrompt, systemPromptFile);
+    if (text) argv.push("-c", `developer_instructions=${tomlString(text)}`);
+  }
+  if (initialPrompt) argv.push(promptArg(initialPrompt));
   return argv;
 }
 
@@ -159,9 +195,10 @@ function buildCatalogArgv(entry, bin, { model, resumeLast, bypass, initialPrompt
   if (resumeLast && entry.resume) argv.push(...entry.resume);
   if (bypass && entry.bypass) argv.push(...entry.bypass);
   const p = entry.prompt;
-  if (initialPrompt && p.mode === "flag") argv.push(p.flag, initialPrompt);
+  if (initialPrompt && p.mode === "flag") argv.push(p.flag, promptArg(initialPrompt));
   if (initialPrompt && p.mode === "argv")
-    argv.push(...(p.separator ? [p.separator] : []), initialPrompt);
+    // A `--` separator already ends the options; without one, guard the prompt.
+    argv.push(...(p.separator ? [p.separator, initialPrompt] : [promptArg(initialPrompt)]));
   return argv;
 }
 
@@ -274,8 +311,18 @@ function spawnRun(args) {
 
   const id = runIdForLane(laneId, slot);
   const startedAt = Date.now();
+  // The workspace's own folders, context files and instructions — read from
+  // its rows here, the one place both spawn paths pass through, never from a
+  // request (server/lib/lane-sources.js).
+  const { addDirs, systemPrompt, systemPromptFile } = require("./lane-sources").launchExtras(
+    laneId,
+    tool
+  );
   const argv = buildArgv(
     {
+      addDirs,
+      systemPrompt,
+      systemPromptFile,
       tool,
       model,
       permissionMode,
@@ -336,6 +383,10 @@ function spawnRun(args) {
   // node`) dies there without the `node` the user's shell would have found.
   const env = {
     AGENTHUB_LANE_ID: String(laneId),
+    // Which pane this is: the CLI's hooks inherit it, so the dashboard learns
+    // which session each pane holds (routes/hooks.js → bindRunSession) — the
+    // sidebar opens a session's own pane by it.
+    AGENTHUB_RUN_ID: id,
     ...(process.env.PATH ? { PATH: process.env.PATH } : {}),
     ...desktopEnv(),
     // A codex pane must read the same home the dashboard reads — its rollout