boot: the errors pane keeps the launch directory, and a typo inside pardes stays one line

Two defects in the +Errors boot, both found by adversarial re-review.

The pane was opened with `dir = ""` — copied from the board's boot buffer,
which can afford it because that platform has no filesystem — so its path came
out `/+Errors` and `paneDir` answered `/`. An output pane's directory is where
a `Grep` from it walks, where its `Newtty` spawns a shell and what its `Save`
prefills, so the boot screen rooted all three at the filesystem root, and the
one word the pane prints resolved against `/` and could never be clicked. The
launch directory rides in `Options.missing` beside the word now, and the test
asserts the pane's path rather than only its contents.

A typo INSIDE pardes stacked a second full-screen UI. The hand-off block above
resolves the word and sends it to the outer instance; `.none` sent nothing and
fell through, which was harmless while the classification below refused it and
became the one input that stacks the UI that block exists to prevent — with no
shell pane in it, so the only way out is `Del`. Its own comment said as much
and was falsified by the +Errors boot. `.none` is refused in that shell now, in
one line and without a stack trace, and the outer session is not told: `Look`
on a word naming nothing is not something to do to somebody else's session.

Also recorded, not fixed: the commonest permission case never reaches the
`.dir` arm this arm's comment defends. `look.isDir` probes with O_DIRECTORY|
O_RDONLY, so a directory you cannot read resolves as `.file` and dies in
`file_pane.open` with `error.OpenFailed` out of `main` — still a trace at a
human, and a different fault than the one fixed here.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_016Q4RATpafkwahrovHQLKRf

1 files changed, 10 insertions, 3 deletions

diff --git a/src/CHANGELOG.md b/src/CHANGELOG.md
index bb7e9ad5..2df1a82e 100644
--- a/src/CHANGELOG.md
+++ b/src/CHANGELOG.md
@@ -64,9 +64,16 @@
   editor at all. A launch that names nothing now boots one `+Errors` pane
   filling the window — acme's own vocabulary for output that came from the
   program rather than from a word somebody clicked — saying `file or directory
-  not found` and the argument AS TYPED. A `chdir` that fails on a directory
-  that really is one is still `BadArgs`: that is a permission problem, not a
-  typo, and the two want different answers.
+  not found` and the argument AS TYPED, in the directory it was typed in — an
+  output pane's directory is where a `Grep` from it walks, where its `Newtty`
+  spawns and what its `Save` prefills, so a pane rooted at `""` would have
+  pointed all three at `/`. A typo INSIDE pardes is refused by that shell in one
+  line instead: the hand-off block that keeps a pardes from stacking a second
+  full-screen UI inside a pane of the first says in its own comment that a word
+  naming nothing must not get through, and an `+Errors` boot would have made a
+  typo the one input that did. A `chdir` that fails on a directory that really
+  is one is still `BadArgs`: that is a permission problem, not a typo, and the
+  two want different answers.
 
 - A filtered terminal costs what an unfiltered one does. `Filter`'s second
   stage asked `RGB.contrast` for every cell it painted, and that call ends in