tide: ask the terminal from inside tmux too

The OSC 11 query opted out under tmux on the assumption it would need the
\ePtmux; passthrough wrapper. It does not, and that assumption cost the
fix precisely where it was wanted: ssh'd into a box inside tmux.

tmux answers OSC 11 from a pane itself, out of the background it queried
from the outer terminal, and it re-queries when that terminal reports a
colour scheme change -- so the value tracks the real window rather than
going stale at tmux start. Measured on tmux 3.7b, the version on both
ends: a pane's query is answered without ever reaching the outer
terminal, and after a colour scheme notification the next query returns
the new background. No tmux configuration is required.

Passthrough is the wrong tool here and stays unused: it is output-only,
so the outer terminal's reply goes to tmux rather than to the pane, and
a wrapped query returns nothing at all.

screen keeps opting out -- untested rather than known broken, and there
the caller falls back to the config files as before.

The live pty suite gains a remote-tmux scenario: config files all dark,
terminal reporting light, the whole thing inside tmux. It fails with the
opt-out restored.

private_dot_config/private_fish/functions/private___tide_terminal_osc_background.fish

@@ -9,11 +9,16 @@ function __tide_terminal_osc_background \
     status is-interactive
     or return 1
 
-    # tmux and screen both need the query wrapped, and each wants it wrapped
-    # differently. Leave those to the caller's config-file path instead of
-    # guessing wrong and eating the user's keystrokes waiting for a reply.
-    set -q TMUX
-    and return 1
+    # tmux needs no special handling: it answers OSC 11 from a pane itself, out
+    # of the background it queried from the outer terminal, and it re-queries
+    # when that terminal reports a colour scheme change -- so the answer tracks
+    # the real window. Do not reach for the \ePtmux; passthrough wrapper here:
+    # that is output-only, the reply goes to tmux rather than to this pane, and
+    # the query then times out having achieved nothing.
+    #
+    # screen is left out because it is untested rather than known broken; there
+    # the caller falls back to reading the config files, as it did everywhere
+    # before this query existed.
     string match -q 'screen*' -- "$TERM"
     and return 1
 

private_dot_config/private_fish/private_tests/private_verify_tide_terminal_events.exp

@@ -18,9 +18,17 @@ set path_label "direct"
 set through_tmux 0
 set mode [expr {[llength $argv] > 0 ? [lindex $argv 0] : "direct"}]
 
-if {$mode eq "tmux"} {
-    set path_label "tmux"
+if {$mode eq "tmux" || $mode eq "remote-tmux"} {
+    set path_label $mode
     set through_tmux 1
+    if {$mode eq "remote-tmux"} {
+        # The ssh-inside-tmux case. tmux answers OSC 11 from a pane out of the
+        # background it holds for the outer terminal, so the query works here
+        # with no wrapping -- but only if nothing opts out of asking.
+        set kitty_config [file join $fixtures kitty-remote-dark]
+        set light_reply "ebeb/e8e8/e4e4"
+        set light_segment "DFDCD8"
+    }
     spawn env TERM=xterm-kitty KITTY_CONFIG_DIRECTORY=$kitty_config \
         tmux -L tide-appearance-test \
         -f "$env(HOME)/.tmux.conf" new-session fish --interactive