feat(c5): add zellij exit-capture logging and shared prune helper

Zellij has no live-stream facility like tmux pipe-pane, so capture is a
one-shot 'zellij action dump-screen --full' run from a fish_exit handler
(conf.d/zellij-logging.fish -> functions/_zellij_dump_log.fish). The C5
guard is checked inside the helper at exit time, so toggling logging
needs no sync_logging coordination — there is no persistent stream.

Extract pruning into functions/_prune_terminal_logs.fish, shared by both
the tmux and zellij helpers. This also fixes a latent bug in the tmux
helper: globbing tmux_*.log directly errored with 'No matches for
wildcard' on the first log in an empty dir. The shared helper globs via
'set' (tolerates no-match) and uses command ls/rm to bypass the eza and
trash C1 shadows.

docs/fish-config.md

@@ -1678,7 +1678,7 @@ silently failing.
 
 #### C5 — Logging and Capture
 
-Four components capture shell output to disk. Disabling
+Five components capture shell output to disk. Disabling
 __fish_config_op_logging skips all capture and removes the logging wrappers.
 
     Component               What it captures
@@ -1687,6 +1687,8 @@ __fish_config_op_logging skips all capture and removes the logging wrappers.
                             ~/.terminal_history/scrollback_YYYY-MM-DD_HH-MM-SS.log
     tmux pane capture       Continuous pane stream via pipe-pane, saved to:
                             ~/.terminal_history/tmux_<session>-w<win>-p<pane>_YYYY-MM-DD_HH-MM-SS.log
+    zellij pane capture     Pane scrollback snapshot on shell exit, saved to:
+                            ~/.terminal_history/zellij_<session>-p<pane>_YYYY-MM-DD_HH-MM-SS.log
     paru wrapper            All paru/AUR output captured to:
                             ~/.terminal_history/paru_YYYY-MM-DD_HH-MM-SS.log
     yay wrapper             All yay/AUR output captured to:
@@ -1701,6 +1703,15 @@ session gets its own log file; a new log is created on each shell start
 tmux_*.log files are pruned (by modification time) to keep the total within
 SCROLLBACK_HISTORY_MAX_FILES, matching the paru/yay wrapper behaviour.
 
+The zellij capture works differently: Zellij has no live output-streaming
+facility like pipe-pane, so the log is taken as a one-shot snapshot when the
+shell exits, via `zellij action dump-screen --full`. A fish_exit handler
+(registered whenever $ZELLIJ is set) writes the pane's full scrollback and
+then prunes old zellij_*.log files the same way. Because the capture happens
+at exit, toggling __fish_config_op_logging takes effect on the next exit with
+no restart or sentinel coordination needed — the C5 guard is re-checked when
+the handler fires.
+
 Logging coordination via sentinel file
 
 C5 uses a sentinel file to synchronize state between the shell and