Fixes from three adversarial reviews, and a destructive one among them

The registry sweep could delete a live socket, anywhere on the filesystem. A
reviewer reproduced it: a socket that is bound but has not reached listen(2)
answers ECONNREFUSED exactly like a dead one -- that window is every server's
startup -- and the sweep then followed the entry's symlink and unlinked
whatever absolute path it named. It now follows a target only into the
directory our own sockets live in and only to a `pardes-9p-*.sock` name, it
re-probes immediately before deleting rather than trusting a probe that is by
then several syscalls old, and a readlink that exactly filled its buffer is
treated as the truncation it is. The test grew a case for an entry whose
target is not ours: the entry goes, the file does not.

Ctrl-V in raw tty mode was a black hole when the yank register was empty --
neither typed nor forwarded -- so vim's visual block, readline's quoted-insert
and every other program's Ctrl-V simply vanished. With nothing to paste the
chord belongs to the program again.

The lone-ESC flush added earlier was dead code. vaxis already returns Escape
for a one-byte 0x1b (`Parser.parseGround` asserts `input.len == 1`), so the
carried byte it waited for can never exist; a reviewer showed a 3 ms gap and a
60 ms gap behaving identically. Removed rather than left to imply a guarantee
it never provided.

A shell whose editor is gone can start one again. Naming a live but
unreachable session made `pardes <file>` exit 1, which let a stale environment
variable lock someone out of their own editor; it falls through to an ordinary
session, as it did before the variable existed.

Also: the macOS ABI check for `pardes_topbar_pane_border_px` had been replaced
by a duplicate of the line above it; `--startup` now fails on a leak the way
every other measurement in that file does, and stops calling its maximum a p95
below twenty samples; the served README and the skill no longer tell you to
write to `data` with `>`, which truncates the whole body before the write
lands; `docs/v9fs.md` described the allocate-on-walk design that was rejected;
and `test/fs.py` keys nesting off `PARDES_PID`, so its forwarding case stops
passing only when the runner happens to be inside a live pardes.

fs-test now reaches its one documented pre-existing failure instead of dying
early. Suite 778/783 with the two known crashes.

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

1 files changed, 3 insertions, 3 deletions

diff --git a/.agents/skills/pardes-9p/SKILL.md b/.agents/skills/pardes-9p/SKILL.md
index 91a8e864..aa856953 100644
--- a/.agents/skills/pardes-9p/SKILL.md
+++ b/.agents/skills/pardes-9p/SKILL.md
@@ -101,7 +101,7 @@ For a file or scratch pane, with `pane=$m/pane/<serial>`:
 | Append text | `echo text >> $pane/body` | `client.write(pane + '/body', b'text\n')` |
 | Replace all text | `echo text > $pane/body` | `client.write(pane + '/body', b'text\n', truncate=True)` |
 | Address a byte range | `echo '#0,#2' > $pane/addr` | `client.write(pane + '/addr', b'#0,#2')` |
-| Replace that range | `echo 'pub fn' > $pane/data` | `client.write(pane + '/data', b'pub fn')` |
+| Replace that range | `printf 'pub fn' >> $pane/data` | `client.write(pane + '/data', b'pub fn')` |
 | Read the selection | `cat $pane/dot` (offsets), `cat $pane/sel` (text) | the same two reads |
 | Select the addressed range | `cp $pane/addr $pane/dot` | `client.write(pane + '/dot', client.read(pane + '/addr'))` |
 | Reload from disk | `echo get > $pane/ctl` | `client.write(pane + '/ctl', b'get\n')` |
@@ -220,8 +220,8 @@ with tempfile.TemporaryDirectory(prefix='pardes-9p-skill-') as directory:
 PY
 ```
 
-`new_pane` walks to `/pane/new` and reads the serial off the directory it
-lands on; `execute` writes one line to a pane's `exec`. Both are in
+`new_pane` opens `/pane/new` and reads the serial it answers; `execute` writes
+one line to a pane's `exec`. Both are in
 `test/fs.py`. For terminal tests, use
 `session(..., tty=True)` and read
 [test/agent_session.py](../../../test/agent_session.py) for bounded interactive