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, 6 insertions, 6 deletions

diff --git a/test/ui_review.py b/test/ui_review.py
index 2b6faa29..a1cdcdeb 100644
--- a/test/ui_review.py
+++ b/test/ui_review.py
@@ -43,7 +43,7 @@ def command(client, serial, text):
     current = client.read(tag)
     start = current.rfind(text.encode())
     client.write(f'/pane/{serial}/event', f'Mx{start} {start + len(text.encode())}\n'.encode())
-    client.write(f'/pane/{serial}/ctl', b'cleartag\n')
+    client.write(f'/pane/{serial}/tag', b'', truncate=True)
     client.write(tag, before[tail_start:])
 
 def new_output(client, before):
@@ -111,7 +111,7 @@ def run(args):
         capture(client, root, '02-find', not args.tty)
         if find_pane:
             (root / 'find-results.txt').write_bytes(client.read(f'/pane/{find_pane}/body'))
-            client.write(f'/pane/{find_pane}/ctl', b'exec Del\n')
+            client.write(f'/pane/{find_pane}/exec', b'Del\n')
         before = panes(client)
         command(client, source, 'Grep CrdsValueLabel')
         grep_pane = require(wait_for(lambda: new_output(client, before)), 'Grep did not return results')
@@ -140,10 +140,10 @@ def run(args):
                 (root / 'symbols-results.txt').write_bytes(client.read(f'/pane/{symbols}/body'))
             capture(client, root, '05-symbols', not args.tty)
             if symbols:
-                client.write(f'/pane/{symbols}/ctl', b'exec Del\n')
+                client.write(f'/pane/{symbols}/exec', b'Del\n')
             offset = original.index(b'CrdsValue {')
             client.write(f'/pane/{source}/addr', f'#{offset},#{offset}'.encode())
-            client.write(f'/pane/{source}/ctl', b'dot=addr\nshow\n')
+            client.write(f'/pane/{source}/dot', client.read(f'/pane/{source}/addr'))
             before = panes(client)
             command(client, source, 'Hover')
             hover = wait_for(lambda: new_output(client, before), args.lsp_wait)
@@ -154,7 +154,7 @@ def run(args):
             # Look focuses the source without changing it; gd then travels through
             # the host's real input parser, unlike tag builtin dispatch above.
             line = original[:original.index(b'impl Sanitize for CrdsValue')].count(b'\n') + 1
-            client.write(f'/pane/{source}/ctl', f'look {source_path}:{line}:19\n'.encode())
+            client.write(f'/pane/{source}/look', f'{source_path}:{line}:19\n'.encode())
             os.write(terminal_handle['input_fd'], b'gd')
             time.sleep(1)
             capture(client, root, '07-definition', not args.tty)
@@ -166,7 +166,7 @@ def run(args):
                 report['lsp'] = info.decode()
             capture(client, root, '08-lsp-info', not args.tty)
             if lsp:
-                client.write(f'/pane/{lsp}/ctl', b'exec Del\n')
+                client.write(f'/pane/{lsp}/exec', b'Del\n')
         for theme in args.themes:
             command(client, source, 'Theme ' + theme)
             capture(client, root, 'theme-' + theme, not args.tty)