feat(maestro): rename a session from the web sidebar

Right-clicking a card opens a custom context menu (rename, spawn similar,
kill). Rename swaps the name for an inline field; Enter commits, Escape and
blur cancel. The tree stops rebuilding while the field is open, so a catalog
delta cannot replace what is being typed into.

Refs #125

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/SIDEBAR.md

@@ -20,6 +20,13 @@ A card is always two lines: **line 1** and **line 2**.
 Line 1 carries no badges. The `⚠ blocked work` badge (#83) and the `exited`
 badge move off this row into line 2.
 
+The name is editable in place (#125). In the web client, right-clicking a card
+opens a context menu whose **rename** entry swaps the name for a text field —
+Enter commits, Escape cancels. The TUI opens the same edit as a prompt, bound
+to `r` in the sidebar by default. Both send `PATCH /api/sessions/:id`; both
+start from the session's own name, never from the command it falls back to,
+and an empty field clears the name so the fallback resumes.
+
 ## Line 2 — meta line (adaptive)
 
 Line 2 always renders — never an empty placeholder row either, since its