The shell runs what it reads, not what a name ends in

A typed word had ".sbx" pasted on the end of it before anything went
looking, which is why "notes.txt" sent the shell after a notes.txt.sbx
that was never going to exist, and why a script could only be started
with "do". The extension was what made a file reachable by name.

Now the word as typed is asked for first and the word with the extension
on it only after that misses. What comes back is dispatched on what is
inside it: SBEX loads and starts, "#!" is read as lines. The loader
already refuses anything that is not SBEX and the script reader already
refuses anything without the shebang, so the two kinds of runnable file
turn each other away and neither has to know the other exists.

The suffix can only ever be a second guess, so a file that is really
there always beats one that would have to be invented and every program
already on a disk still starts by the short name people type for it. It
costs a second walk of each directory when a word is not found in it.

Tab completion offers a file under the name it actually has, and the
suffix stripper is gone: a first word can now be any file at all, and
offering only the ones ending .sbx would hide the scripts.

The video capture windows moved out a hundred thousand cycles, because
starting Lander now walks four names where it walked two.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW

Tests/expected/cosmosInvoke.out

@@ -11,15 +11,27 @@ finished
 > dir
 Say.sbx                 156
 dir.sbx                 156
+Greet                   156
 notes.txt               21
 notes.sbx               21
-4 files
+hello.sh                38
+Apps                    <dir>
+6 files, 1 directory
+> Greet a program with no extension
+it says: a program with no extension
+finished
+> hello.sh
+> echo a script, started by its name
+a script, started by its name
+> away.sh
+> echo a script from the system place
+a script from the system place
 > notes
-not a program
+that is not a program or a script: notes
 > notes.sbx
-not a program
+that is not a program or a script: notes.sbx
 > notes.txt
-I do not know: notes.txt
+that is not a program or a script: notes.txt
 > nosuchprogram
 I do not know: nosuchprogram
 > abcdefghijklmnopqr