feat(tabs): live tab resync + adopt-by-targetId + open --reuse-tab (#21)

Multi-session over one relayed Chrome had a tab-identity fracture: each daemon
discovered targets ONCE at connect and assigned its own t<N> indices, so a tab
filled in session A was unreachable from session B — B saw a disjoint/blank set
and rebinding via 'open' piled up duplicate tabs. A stranded, still-filled tab
could not be finished from any other session.

- 'tab list' now re-syncs the live target set on every call: adopts tabs other
  sessions opened (or that re-attached after a cross-process nav), drops gone
  ones (clears phantom rows), and refreshes url/title from each live tab via
  Target.getTargetInfo (the relay only stamps target_info on attach, so it goes
  stale/blank after navigation — which made rows indistinguishable).
- 'tab list --full' now prints each tab's stable CDP targetId. Unlike t<N>
  (per-session, reassigned each connect), targetId is stable across every session
  on the relayed Chrome.
- 'tab <targetId>' adopts a specific pre-existing tab — including another
  session's — WITHOUT reloading, so a half-filled form survives. handle_tab_switch
  resyncs first, then resolves a raw targetId before falling back to t<N>/label.
- 'open <url> --reuse-tab' (alias --reuse) switches to an existing tab already on
  that URL (matched by origin+path, ignoring volatile query/fragment) instead of
  spawning a duplicate.

Verified live over the extension relay: a fresh session's 'tab list --full' lists
the user's real tabs with correct titles + full URLs + targetIds, and
'tab <targetId>' lands on and reads the exact stranded Rakuten account-recovery
form from the report. Unit tests cover URL normalization + --reuse-tab parsing;
full suite green. Docs: --help Tabs section + core skill multi-session guidance.

cli/src/output.rs

@@ -512,6 +512,14 @@ pub fn print_response_with_opts(resp: &Response, action: Option<&str>, opts: &Ou
                 } else {
                     println!("{} [{}] {} - {}", marker, tab_id, title, url);
                 }
+                // `--full` also surfaces the stable cross-session CDP targetId so
+                // a stranded tab can be adopted from another session via
+                // `tab <targetId>` (issue #21).
+                if full {
+                    if let Some(target_id) = tab.get("targetId").and_then(|v| v.as_str()) {
+                        println!("      {}", color::dim(&format!("target: {}", target_id)));
+                    }
+                }
             }
             return;
         }
@@ -3116,7 +3124,12 @@ Storage:
   storage <local|session>    Manage web storage
 
 Tabs:
-  tab [new|list|close|<n>]   Manage tabs
+  tab [new|list|close|<ref>] Manage tabs (<ref> = t<N>, a label, or a CDP targetId)
+  tab list --full            Full URLs + stable cross-session targetId per tab
+  tab <targetId>             Adopt a specific tab (incl. another session's) by its
+                             stable targetId, no reload — preserves in-page state
+  open <url> --reuse-tab     Reuse an existing tab on that URL instead of spawning
+                             a duplicate (matches origin+path; preserves state)
 
 Diff:
   diff snapshot              Compare current vs last snapshot