feat: render multiple status icons per one tab

[0xAndoroid]

If there are multiple sessions running in the same tab, multiple status icons are shown. Icons follow the geometry of the panes of the layout.

[0xAndoroid]

Didn't see #6 while opening this one.

[ishefi]

Thanks for tackling this. The geometry-based ordering (top-to-bottom, left-to-right via pane_manifest) and the is_plugin filter are the right call, better than ordering by pane_id. The single-session guard on elapsed_time is also a nice touch.

That said, PR #6 covers a wider set of issues this one leaves open:

• Tab width flicker as wide glyphs (⚡⚙▶⚠) swap with narrow ones. Render one symbol per Claude pane within each tab #6 fixes this with a fixed 2-col symbol cell and variation-selector-aware width.
• Whole-tab flash vs. per-symbol flash. Render one symbol per Claude pane within each tab #6 scopes the pulse to the affected pane.
• Click model: only Waiting markers are independently clickable here; Render one symbol per Claude pane within each tab #6 makes every symbol its own focus target via a ClickAction enum, which is more consistent.
• Plus a merge_sessions ordering fix (last_ts_ms) and a tightened overflow guard that become more important once we render multiple symbols per tab.

I'm leaning toward landing #6 as the base and porting your geometry-ordering + is_plugin filter on top. Would you be open to that? Happy to credit the ordering approach to you in the follow-up. If you'd rather, the alternative is rebasing this PR to pick up the fixed-cell rendering + ClickAction refactor from #6.