One rule for failing builtins: the write fails, one err, no msg

A builtin that failed through a ctl failed the write and logged its err,
but through look, exec, tagexec or a column's exec it only said so on the
message row, logged as a msg, and the write succeeded. Now every click
write runs its builtin as a ctl line does (ctl.captured): a failure fails
the write, with its words (EINVAL for malformed input, else EIO or what
the words name), logs one err and no msg or announcement. get's Modified
and a look miss are shown but logged once, as their err. A control
character's refusal names its reason, a failed click reads back nothing,
and look never reads back a pane closed since. The special case for a
cut-short Edit through exec goes (the rule covers it); fs.md's table of
exceptions becomes the one rule, as does the skill.

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

1 files changed, 4 insertions, 0 deletions

diff --git a/src/fs.zig b/src/fs.zig
index cb89648c..71e2cbad 100644
--- a/src/fs.zig
+++ b/src/fs.zig
@@ -1274,6 +1274,10 @@ pub const Namespace = struct {
     /// A ctl write's failure is being said: its err record logs it, so
     /// no msg does (Messages.reportFailure).
     unlogged: bool = false,
+    /// A 9P write of clicks (look, exec, tagexec, a column's exec) is running
+    /// one: a builtin's failure is the write's, as a ctl line's is (no_prompt,
+    /// which also refuses prompts, which a click may open).
+    capturing: bool = false,
     /// A 9P request is being served (Pardes.serveFs): a prompt it opens is
     /// a question for the log (`ask`), answered with `answer`.
     serving: bool = false,