Plan 9 idiom for the control filesystem, and the regressions a624a56 left

The 9P tree stops being a command language wearing a filesystem. /new
created a pane as a side effect of a *read*; it is now Tcreate in /pane,
with Tremove to close, which cloud9's engine has always supported and the
editor never declared: tree.zig now says
`features = .{ .create = true, .remove = true }`. Eleven pane ctl verbs
become files that can be read as well as written -- dot, limit, dirty,
mark, scroll, look, exec -- leaving ctl with `get`, the one verb no file
would say better. Root /ctl splits into a read-only /status and the
/look and /exec files whose write IS the click. stat carries real sizes
where it used to answer 0, and qid versions track a pane's revision, so a
client can poll for change without re-reading the body.

Commit a624a56 moved raw-tty keys to an early-return branch that knew only
Ctrl-B and bare Escape, and in the same edit deleted the paste branch below
it. That cost Shift-Escape (the unconditional way out of tty mode) and both
paste chords: Ctrl-V and Ctrl-Shift-V reached the child as keystrokes, so an
agent CLI running in a pane took Ctrl-V for its image-paste binding and
answered "No image found in clipboard". Both are restored, with tests.

Nested detection was not subtly broken but deleted: 60367d8 removed
nested.zig's process-ancestry walk and left "am I inside pardes" derived from
PARDES_FORWARD_LOOK, which read "0" both for --nested and for "the listener
did not come up". PARDES_PID now answers that question on its own, checked
with kill(pid, 0); PARDES_9P and PARDES_PANE answer how to reach it; the flag
is gone. The posted-9P registry also self-heals now -- a session that aborts
cannot unlink its own socket, so posting sweeps entries whose target refuses
a connection, symlinks only and on a definite ECONNREFUSED only.

Elsewhere: tty scrolling is sticky-bottom, following new output only from
the last row, with typing and entering raw mode snapping back to live; the
boot layouts are a Boot enum instead of a chain of ifs, and the bare tty
startup (Boot.tty, which main.zig names) opens an empty text pane under the
shell while tests keep Boot.tty_shell; builtins announce themselves on the
message row under a Verbose setting that is on by default; Config prints
each setting the way you would type it back, so WindowOpacity 70 rather than
"WindowOpacity: 70%"; LocationsConfig opens its window only when called bare;
every tagline puts the word that closes the thing last, and a column now
outlives its panes -- closing the last one leaves an empty pane, and only
Delcol, newly on the column tagline, takes the column away.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

1 files changed, 14 insertions, 4 deletions

diff --git a/docs/config.md b/docs/config.md
index a55aef1c..04b0fd82 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -111,6 +111,10 @@ Workspace, column and pane command text can be edited directly; see
 `ColumnTags` toggles the column command row in both GUI and TTY; it is on by
 default. Add `ColumnTags` to startup configuration to reclaim that row on a
 compact screen. Hiding it preserves your custom column commands.
+`Verbose` toggles the message-row announcement every builtin makes of its own
+name before it runs; it is on by default, and the builtins that own the message
+row themselves (`Msg`) never announce. Turning it off leaves the row to the
+messages a builtin chooses to write.
 `SyntaxBold` toggles bold syntax keywords; it is off by default. These
 settings are shared by GUI and TTY, and `Config` reports their current
 states. Like `Colors` and `Wrap`, these commands take no argument and invert
@@ -334,10 +338,16 @@ The installed `pardes-v9fs` helper lives beside the editor; development builds
 can set `PARDES_V9FS_HELPER` to its absolute path. See [v9fs.md](v9fs.md).
 
 Ctrl-B switches between raw TTY and editor mode. Plain Escape at a detected
-shell prompt hops back to the previous pane. Other keys, including Ctrl-O, Ctrl-W,
-paste shortcuts, and modified Escape belong
-to the child. Use `Mode` in the pane tag to return to editor
-mode in place. Desktop paste events still feed the terminal.
+shell prompt hops back to the previous pane. Other keys, including Ctrl-O,
+Ctrl-W and modified Escape, belong to the child. Use `Mode` in the pane tag to
+return to editor mode in place. Desktop paste events still feed the terminal.
+
+The paste chords are the exception the window keeps. Ctrl-V types the yank
+register at the program, and Ctrl-Shift-V asks the desktop for its clipboard
+and types that; both go through the program's bracketed paste when it has
+asked for one. Neither reaches the child as a keystroke, so an application
+that would otherwise answer Ctrl-V by reading the system clipboard itself
+never gets the chance to read the wrong thing.
 
 `Font` and `FontSel` exist ONLY in the SDL GUI and native macOS builds — a
 terminal's font belongs to its emulator and a browser's to the page — so a