The default Shell is $SHELL, else /bin/sh

With no Shell set, pardes ran fish, which a box may not have and a user
may not use. The default is now the user's login shell ($SHELL), else
/bin/sh; an explicit Shell still overrides it. The tests pin their own
shell (snapshots bash, the python suites /bin/sh or bash) and pass with
SHELL unset; the Config report and docs say where the default comes from.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

2 files changed, 3 insertions, 2 deletions

diff --git a/docs/config.md b/docs/config.md
index 40d0fb24..93190556 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -46,7 +46,8 @@ the browser still applies the compiled percentage to its DOM glyphs.
 The startup path is printed whether or not a file exists — that is usually when
 it is most useful — and is ordinary selectable text, so a right click on it
 opens the file. Shell follows the same requested/effective/pending model as
-Font. `Compiled default shell` is the command built into the binary; `Shell
+Font. `Default shell` is the one used while no `Shell` is set: `$SHELL`, the
+user's login shell, else `/bin/sh`; an explicit `Shell` overrides it. `Shell
 effective (last spawn)` is the executable the native host really chose after
 installation lookup and fallback. A changed request remains pending until a
 terminal is spawned, because the core does not resolve native executables.
diff --git a/docs/fs.md b/docs/fs.md
index a93137bb..95ab4de0 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -304,7 +304,7 @@ same tree without leaving the process.
   is typed into that shell (and a terminal whose shell exits, `exit` typed
   or run, closes its pane). From anywhere else -- a file, a scratch, a tag,
   a terminal whose tty a program holds -- it runs as a command pane: a
-  terminal whose child is the root ctl's `Shell` (fish unless set) run
+  terminal whose child is the root ctl's `Shell` ($SHELL, else /bin/sh, unless set) run
   with `-c` and the line, in the pane's directory, with job control on
   (bash, sh, dash, zsh, ksh `-m`; fish `status job-control full`),
   which shows its output and then `exit N` (its tag reads `<dir> (<line>)