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, 7 insertions, 7 deletions

diff --git a/test/appearance_gallery.py b/test/appearance_gallery.py
index 0fa12136..48c0ea1b 100644
--- a/test/appearance_gallery.py
+++ b/test/appearance_gallery.py
@@ -82,7 +82,7 @@ def run(args):
         right = require(wait_for(lambda: next((s for s in panes(client) if s not in before), None)), 'right column missing')
         client.write(f'/pane/{right}/name', f'{root / "Review"}\n'.encode())
         client.write(f'/pane/{right}/body', PREFERENCE_NOTES if args.theme_selector else NOTES, truncate=True)
-        client.write(f'/pane/{right}/ctl', b'clean\n')
+        client.write(f'/pane/{right}/dirty', b'0\n')
         before = set(panes(client))
         command(client, right, 'Tty')
         terminal = require(wait_for(lambda: next((s for s in panes(client) if s not in before), None)), 'terminal missing')
@@ -94,12 +94,12 @@ def run(args):
             command(client, right, 'Config')
             pane = require(wait_for(lambda: next((s for s in panes(client) if s not in before), None)), 'Config output missing')
             text = client.read(f'/pane/{pane}/body').decode()
-            client.write(f'/pane/{pane}/ctl', b'exec Del\n')
+            client.write(f'/pane/{pane}/exec', b'Del\n')
             return text
 
         settings = config_report()
-        require('Font effective size: 18.00 pixels' in settings, 'configured font size not applied: ' + settings)
-        require('TaglineSize: 80' in settings, 'configured tag size missing')
+        require('Font effective size 18.00 pixels' in settings, 'configured font size not applied: ' + settings)
+        require('TaglineSize 80' in settings, 'configured tag size missing')
         (root / 'effective-config.txt').write_text(settings)
         report['font_effective_pixels'] = 18
         report['tagline_percent'] = 80
@@ -135,7 +135,7 @@ def run(args):
             command(client, right, 'Theme ' + theme)
             if args.theme_selector:
                 # Keep both quiet active gutter ink and vivid comments in view.
-                client.write(f'/pane/{source}/ctl', f'look {source_path}:117\n'.encode())
+                client.write(f'/pane/{source}/look', f'{source_path}:117\n'.encode())
             take_frame('classic-' + theme)
             if args.theme_selector:
                 frame = client.screen()
@@ -171,14 +171,14 @@ def run(args):
                     'ThemeSel did not open at native first entry')
             take_frame('theme-selector')
             report['native_themes_first'] = True
-            client.write(f'/pane/{selector}/ctl', b'exec Del\n')
+            client.write(f'/pane/{selector}/exec', b'Del\n')
             command(client, terminal, 'Collapse')
         for pet in (() if args.skip_pets else ('cat', 'frog', 'off')):
             command(client, right, 'Pet ' + pet)
             settings = config_report()
             require('Pet: ' + pet + '\n' in settings, 'pet setting not applied')
             # Returning focus to the source closes all transient report state.
-            client.write(f'/pane/{source}/ctl', f'look {source_path}:1\n'.encode())
+            client.write(f'/pane/{source}/look', f'{source_path}:1\n'.encode())
             take_frame('pet-' + pet)
             if pet != 'off':
                 frame = client.screen()