feat(owt): share the main checkout's omo memory with workspaces

omo keys project memory by folder path, so each workspace started with an
empty store. owt new and owt open now link the workspace's memory id to the
main checkout's store, and owt done and owt rm remove the link.

.local/bin/owt

@@ -58,6 +58,9 @@ Usage (run from anywhere inside the repo):
                   session inside the workspace can finish first
         The omo slash command /owt-done syncs Linear and then runs this.
 
+Workspaces share the main checkout's omo memory: owt new and owt open link the
+workspace's memory id to the main store, and owt done and owt rm remove the link.
+
 Env:
   OWT_ROOT    Workspace root (default: ~/worktrees)
   OWT_AGENT   Agent command (default: omo; must accept omo's --name and
@@ -77,6 +80,40 @@ main_root() {
 
 repo_name() { basename "$(main_root)"; }
 
+memory_agents_dir() { printf '%s/agents\n' "${OMO_MEMORY_HOME:-$HOME/.omo/memory}"; }
+
+# omo's default memory id for a folder: its name as a slug, plus the first
+# 8 hex chars of sha256 of its path.
+memory_id() {
+  local path="$1" slug
+  slug="$(basename "$path" | tr '[:upper:]' '[:lower:]' | sed -E 's/[^a-z0-9]+/-/g; s/^-+//; s/-+$//' | cut -c1-40 | sed -E 's/-+$//')"
+  printf '%s-%s\n' "${slug:-agent}" "$(printf '%s' "$path" | shasum -a 256 | cut -c1-8)"
+}
+
+# Point the workspace's memory id at the main checkout's store, so omo sessions
+# in the workspace read and write the project's memory.
+link_memory() {
+  local agents main ws
+  agents="$(memory_agents_dir)"
+  main="$(memory_id "$(cd "$(main_root)" && pwd -P)")"
+  ws="$(memory_id "$(cd "$1" && pwd -P)")"
+  [[ -L "$agents/$ws" ]] && return 0
+  if [[ ! -d "$agents/$main" ]]; then
+    say "no omo memory for $(repo_name) yet (run omo once in the main checkout); memory not shared"
+  elif [[ -e "$agents/$ws" ]]; then
+    say "workspace already has its own memory store $agents/$ws; memory not shared"
+  else
+    ln -s "$main" "$agents/$ws"
+    say "sharing omo memory $main"
+  fi
+}
+
+unlink_memory() {
+  local link
+  link="$(memory_agents_dir)/$(memory_id "$(cd "$1" && pwd -P)")"
+  if [[ -L "$link" ]]; then rm "$link"; fi
+}
+
 # owner/repo from the origin URL (https or ssh form).
 repo_slug() {
   local url
@@ -214,6 +251,7 @@ cmd_new() {
   git -C "$root" worktree add --no-track -b "$branch" "$dir" "$base"
 
   copy_env_files "$root" "$dir"
+  link_memory "$dir"
   if [[ $install -eq 1 ]]; then install_deps "$dir"; fi
   say "workspace '$name' ready at $dir on $branch"
   if [[ $open -eq 1 ]]; then
@@ -230,6 +268,7 @@ cmd_open() {
   [[ -n "$name" ]] || die "usage: owt open <name>"
   dir="$(ws_dir "$name")"
   [[ -d "$dir" ]] || die "no workspace at $dir"
+  link_memory "$dir"
   launch "$name" "$dir"
 }
 
@@ -269,6 +308,7 @@ cmd_rm() {
   [[ -d "$dir" ]] || die "no workspace at $dir"
   branch="$(git -C "$dir" symbolic-ref --quiet --short HEAD || true)"
 
+  unlink_memory "$dir"
   if [[ $force -eq 1 ]]; then
     git -C "$root" worktree remove --force "$dir"
   else
@@ -373,6 +413,7 @@ cmd_done() {
     say "kept remote branch $branch because it is not merged"
   fi
 
+  unlink_memory "$dir"
   git -C "$root" worktree remove --force "$dir"
   say "removed $dir"
   if [[ -n "$branch" ]]; then