feat(v0.5.4): info Session block

Add a Session block to ctask info output, surfacing the workspace
session lease state derived from SessionStatus. Inserted between Path
and any launch-dir fields so the new content is visually distinct
from both blocks.

Format: state on the header line, then indented Mode / Owner / Attach
/ Note rows aligned at column 14. The Owner line omits the hostname
when it matches the local machine. The Attach hint surfaces only for
active+persistent sessions and uses invocationName() so the suggested
command reflects the user's actual invocation. Malformed leases
render as stale with a single-line diagnostic and no Mode/Owner/Attach
rows so we never display fields parsed from a broken file.

Exposes session.CurrentHostname() so the cmd layer has a single
source of truth for the local-vs-remote hostname check.

internal/session/lease.go

@@ -81,6 +81,12 @@ func currentHostname() string {
 	return h
 }
 
+// CurrentHostname is the exported form of currentHostname for callers in
+// cmd/ that need to compare a lease's recorded hostname against the local
+// machine (e.g., info's Owner-line "omit when local" rule). Keeps a
+// single source of truth for the unknown-fallback semantics.
+func CurrentHostname() string { return currentHostname() }
+
 // currentTerminal is a best-effort terminal identifier based on common env vars.
 // Returns "unknown" if none are set.
 func currentTerminal() string {