Adopt libtmux 0.56.0 wrappers, drop raw cmd() escape hatches

Background

libtmux v0.56.0 (PR #653) lands ~50 new public methods covering tmux commands that previously required dropping down to Server.cmd(...). The release notes call this out explicitly:

Net result: callers no longer need to drop down to Server.cmd(...) for the commands tmux ships out of the box.

libtmux-mcp is one of those callers. This issue tracks adopting the new wrappers across the 15 call sites that have direct replacements, plus the dependency floor bump that unlocks them.

Prerequisite

Bump libtmux>=0.55.1,<1.0 → libtmux>=0.56.0,<1.0 in pyproject.toml

Migration checklist

Each row pairs an MCP call site (left) with the libtmux 0.56.0 wrapper that replaces it (right, permalinked to the v0.56.0 tag).

Cluster 1 — Pane lifecycle / respawn

src/libtmux_mcp/tools/pane_tools/lifecycle.py:172 — pane.cmd(\"respawn-pane\", *argv) → Pane.respawn. Deletes the stopgap comment block at lifecycle.py:153-162 and the manual if result.stderr: branch (Pane.respawn raises LibTmuxException directly).

Cluster 2 — Copy mode / pipe / clear_history

src/libtmux_mcp/tools/pane_tools/copy_mode.py:60 — pane.cmd(\"copy-mode\") → Pane.copy_mode
src/libtmux_mcp/tools/pane_tools/copy_mode.py:62-68 — pane.cmd(\"send-keys\", \"-X\", \"-N\", str(n), \"scroll-up\") → Pane.send_keys(copy_mode_cmd=\"scroll-up\", repeat=scroll_up, enter=False)
src/libtmux_mcp/tools/pane_tools/copy_mode.py:113 — pane.cmd(\"send-keys\", \"-X\", \"cancel\") → Pane.send_keys(copy_mode_cmd=\"cancel\", enter=False)
src/libtmux_mcp/tools/pane_tools/pipe.py:78 — pane.cmd(\"pipe-pane\") → Pane.pipe()
src/libtmux_mcp/tools/pane_tools/pipe.py:86 — pane.cmd(\"pipe-pane\", \"cat ...\") → Pane.pipe(\"cat ...\")
src/libtmux_mcp/tools/pane_tools/io.py:241 — pane.cmd(\"clear-history\") → Pane.clear_history(). Keep the explicit two-call structure (do NOT use Pane.reset() — it's still broken upstream per libtmux #650); the line above (pane.cmd(\"send-keys\", \"-R\")) stays as-is.

Cluster 3 — Buffer I/O

src/libtmux_mcp/tools/buffer_tools.py:275 — pane.cmd(\"paste-buffer\", \"-b\", n, ...) → Pane.paste_buffer(buffer_name=cname, bracket=bracket). Eliminates a duplicate -t pane_id (libtmux's Pane.cmd already injects it).
src/libtmux_mcp/tools/pane_tools/io.py:334 — pane.cmd(\"paste-buffer\", ...) → Pane.paste_buffer(buffer_name=..., bracket=bracket, delete_after=True)
src/libtmux_mcp/tools/pane_tools/io.py:342 — server.cmd(\"delete-buffer\", \"-b\", buffer_name) → Server.delete_buffer(buffer_name=buffer_name)
src/libtmux_mcp/server.py:264 — server.cmd(\"delete-buffer\", \"-b\", name) → Server.delete_buffer(buffer_name=name)

Cluster 4 — Session window navigation

src/libtmux_mcp/tools/session_tools.py:313-329 — the next/previous/last-window dispatch block → Session.next_window / Session.previous_window / Session.last_window. Each wrapper returns the new active Window directly and raises on stderr, removing the if proc.stderr: branch and the post-call session.active_window re-fetch.

Cluster 5 — Layout / select / swap / display-message

src/libtmux_mcp/tools/pane_tools/layout.py:74 — window.cmd(\"display-message\", \"-p\", \"#{window_zoomed_flag}\") → window.refresh(); is_zoomed = window.window_zoomed_flag == \"1\" (no round trip; just read the ORM attribute).
src/libtmux_mcp/tools/pane_tools/layout.py:174 — server.cmd(\"select-pane\", target=target_pane.pane_id) → target_pane.select() (already a method on Pane; no new wrapper needed, but the migration belongs in this cleanup).
src/libtmux_mcp/tools/pane_tools/layout.py:221 — server.cmd(\"swap-pane\", \"-s\", src, \"-t\", tgt) → Pane.swap (called as source.swap(target=target) after resolving target to a Pane).
src/libtmux_mcp/tools/pane_tools/meta.py:66 — pane.cmd(\"display-message\", \"-p\", format_string) → Pane.display_message(format_string, get_text=True)
src/libtmux_mcp/tools/pane_tools/meta.py:162 — pane.cmd(\"display-message\", \"-p\", fmt) → Pane.display_message(fmt, get_text=True)

Out of scope (no wrapper yet)

These sites have no clean wrapper in 0.56.0 and should remain .cmd(...):

src/libtmux_mcp/_utils.py:159 — server.cmd(\"display-message\", \"-p\", \"#{socket_path}\"). Server has no display_message wrapper (only Pane does).
src/libtmux_mcp/tools/server_tools.py:181, 251 — same: server-scoped #{version} read.
src/libtmux_mcp/tools/pane_tools/search.py:206 — list-panes -f #{C/...} C-filter expression; server.panes doesn't expose the -f shortcut.
src/libtmux_mcp/server.py:256 — list-buffers -F #{buffer_name}. Server.list_buffers() returns tmux's default formatted lines (name: 5 bytes: ...), not raw names; keep the -F form until upstream adds a format= kwarg.

Suggested execution

Per the project's per-phase commit workflow, each cluster above maps to one phase: implement, run the full verification chain (just ruff check, just ruff format, just mypy, just test, just build-docs), commit, then proceed to the next cluster. All five clusters land in one PR.