o: support colon separator and quoted names in context arg

- session:agent works as alternative to session/agent
- Colon takes precedence (allows slashes in session names)
- Quoted arguments with spaces now work: o "my session:agent" prompt
- Removed set -- $* which broke quoted arguments
- Updated help with examples

data/scripts/o

@@ -5,8 +5,11 @@
 #   o <cmd>                     Root level
 #   o <session> <cmd>           Session level
 #   o <session>/<agent> <cmd>   Agent level
+#   o <session>:<agent> <cmd>   Agent level (colon separator)
 #
-# The slash in session/agent disambiguates context level.
+# The slash or colon in session/agent disambiguates context level.
+# Use colon when session or agent names contain slashes.
+# Names with spaces can be quoted: o "my session:my agent" prompt
 #
 # Subcommands:
 #   read   <path>         Read a file (-l to loop)
@@ -476,8 +479,11 @@ Context is determined by the first argument:
   o <cmd>                     Root level
   o <session> <cmd>           Session level
   o <session>/<agent> <cmd>   Agent level
+  o <session>:<agent> <cmd>   Agent level (colon separator)
 
-The slash in <session>/<agent> disambiguates context level.
+The slash or colon in session/agent disambiguates context level.
+Use colon when session or agent names contain slashes.
+Names with spaces can be quoted: o "my session:my agent" prompt
 
 Paths starting with / are root-relative (ignore context):
   o myproj ls /bypass         List root bypass/ even in session context
@@ -497,7 +503,7 @@ Commands (availability depends on context):
     deny [id]             Deny pending bypass request
     read/write <path>     Access session files
 
-  Agent level (o <session>/<agent> ...):
+  Agent level (o <session>/<agent> or <session>:<agent> ...):
     new [cwd]             Create session (if needed) and agent
     ls                    List agent files
     ctl <cmd>             Agent control (stop, compact, model, etc.)
@@ -519,6 +525,8 @@ Commands (availability depends on context):
 Examples:
   o ls                        # list root (sessions, models)
   o myproj/coding new         # create session+agent (cwd=$PWD)
+  o myproj:coding new         # same, using colon separator
+  o "my proj:coding" new      # session name with space
   o myproj/coding new ~/src   # create with specific cwd
   o myproj ls                 # list session contents
   o myproj/coding prompt      # interactive prompt
@@ -560,23 +568,40 @@ dispatch_cmd() {
 }
 
 # Parse context from first argument
+# Supports:
+#   session/agent     (slash separator)
+#   session:agent     (colon separator)
+#   "session name/agent"  (quoted with spaces)
+#   session\ name/agent   (escaped spaces)
 parse_context() {
     local arg="$1"
-    if [[ "$arg" == */* ]]; then
-        # session/agent format
+    
+    # Check for colon or slash separator
+    # Colon takes precedence if both present (allows session with / in name)
+    if [[ "$arg" == *:* ]]; then
+        CTX_SESSION="${arg%%:*}"
+        CTX_AGENT="${arg#*:}"
+    elif [[ "$arg" == */* ]]; then
         CTX_SESSION="${arg%%/*}"
         CTX_AGENT="${arg#*/}"
-        PREFIX="session/$CTX_SESSION/agent/$CTX_AGENT"
     else
         # session only
         CTX_SESSION="$arg"
+        CTX_AGENT=""
+    fi
+    
+    # Build prefix
+    if [[ -n "$CTX_AGENT" ]]; then
+        PREFIX="session/$CTX_SESSION/agent/$CTX_AGENT"
+    else
         PREFIX="session/$CTX_SESSION"
     fi
 }
 
-# Re-split arguments: handles quoted invocations (e.g., acme passes
-# the entire command as a single-quoted string).
-set -- $*
+# Note: We do NOT re-split arguments here. The previous `set -- $*` was
+# removed because it breaks quoted arguments with spaces. If callers pass
+# a single quoted string, they should use eval or proper quoting.
+# For acme integration, the calling script should handle argument parsing.
 
 # Main dispatch
 if [[ $# -lt 1 ]]; then