PETSCII (Commodore 64/128) terminal support

A dedicated rendering path for real C64/128 hardware and PETSCII
terminal emulators (SyncTERM's C64 mode, Novaterm, CCGMS, 64NIC+).
Completely separate from the ANSI telnet/SSH/rlogin path — PETSCII
isn't ANSI, so there's no shared cursor-addressing, no color codes,
no lightbar selectors. Everything here is plain text, numbered
menus, and single-key prompts, built by hand in
anetbbs/features/petscii_ui.py.

There is a matching player-facing wiki page (petscii slug) seeded
by anetbbs/wiki/seed.py — same content, aimed at players connecting
from a real C64 rather than sysops. Update both if you change how
this works.

Connecting

Two dedicated ports, one per screen width — matching Synchronet's own
"40 Column PETSCII Support" / "80 Column PETSCII Support" convention.
Both are off by default; a sysop opts in per-width:

Every connection on a PETSCII port is PETSCII, at that port's fixed
width, unconditionally — there's no telnet TTYPE auto-detection,
because real C64 clients mostly don't announce themselves usefully
that way. Users just pick the port matching their screen/emulator
setting. See docs/INSTALL.md §10 and docs/PORTS.md for the
enable/firewall steps.

Both listeners run inside the same unified anetbbs.service process
as telnet/SSH/rlogin (anetbbs/main.py starts one PetsciiServer
task per enabled width) — not a separate systemd unit.

What's available

Reuses the same underlying data models (Board/Post,
EchoArea/EchomailMessage, PrivateMessage, FileArea/
FileUpload, UserSession, User) as the ANSI screens — never their
rendering code. Covered:

• Message boards — browse, read threads, post, reply
• Echomail — network-first picker (pick the network, then its
  areas — not one combined list across every joined network), read,
  compose/reply, XMODEM-free (message bodies only)
• Private messages — inbox, read, compose/reply
• File areas — browse, view extended description on demand (E),
  download over XMODEM (reuses features/xfer.py's
  send_file() — same transfer code the ANSI side uses; PETSCII
  connections are plain telnet sockets, so no protocol difference)
• Who's online
• Profile — view and edit
• Number Guessing — the one built-in game offered here. Pure
  session I/O (guess a number, get higher/lower feedback), no cursor
  addressing at all, so it's the only game from the wider Game Center
  catalog that has a PETSCII-safe implementation
  (features/games.py's GameManager.play_number_guess(), reused
  directly rather than reimplemented)
• Logoff

Deliberately absent (not shown, not marked "unavailable," just not
offered): door games, ANetCRAFT, DOOM/Duke3D, MRC chat, IRC — none of
those have a plain-text-only path, same reasoning that already
excludes Wall/ANSI-art screens from PETSCII sessions.

Text rendering rules

• ANSI-art bodies get stripped, not garbled. File descriptions,
  echomail/PM/board bodies containing CP437/Unicode box-drawing art
  (common in FILE_ID.DIZ-style banners) collapse to spaces before
  display — the PETSCII encoder has no representation for those
  characters and would otherwise render walls of ?.
• Word-wrap, not hard-break. All body text and status/prompt
  lines wrap at word boundaries to the session's actual width (40 or
  80), never mid-word.
• Never fill a row to exactly the terminal width. Real hardware
  auto-wraps a full-width line on its own, which eats a blank line if
  the software also tries to newline after it — every render budgets
  width - 1.
• Pagination: long lists/bodies page at a fixed line count with
  M=more, B=back (previous page), Q=quit-to-menu.

Custom PETSCII menus (sysop-buildable)

Sysops can replace the hardcoded Phase 1 menu with fully custom
menus at /admin/petscii-menus/ — a completely separate tree
from the ANSI custom-menu system (BbsMenu/BbsMenuItem), not a
shared one. Most ANSI action types (art, sixel, chat, most doors)
have no PETSCII equivalent, so a shared tree would mean items
silently missing on this side; a dedicated PetsciiMenu/
PetsciiMenuItem model pair gives full layout control instead.

• If no PetsciiMenu has is_default=True, PETSCII sessions fall
  back to the hardcoded Phase 1 menu unchanged — this feature is
  opt-in, not a replacement.
• Each menu item has a hotkey, label, min_access, sort_order,
  visibility flag, and an action_type — deliberately a much smaller
  set than the ANSI side, limited to what petscii_ui.py actually
  has a plain-text handler for:

• Admin routes: list (/), create (/new), edit (/<id>/edit),
  delete (/<id>/delete), add/edit/delete item, and spawn-submenu
  (/<id>/spawn-submenu — creates a new empty PetsciiMenu and a
  goto item pointing to it in one step, for building out a menu
  tree without leaving the editor).

Real-hardware lessons baked into this code

Built and refined against real C64/128 hardware over several rounds
of live testing, not just terminal emulators. A few non-obvious
things this rendering path handles that a naive ANSI-style port
would get wrong:

• Keyboard charset timing. A real C64 keyboard's PETSCII byte
  code for a letter depends on which charset ROM is selected — a
  KERNAL keyboard-decode difference, not just display. The
  lowercase-charset switch must be sent before session.start()
  (before the login screen), or every password typed during login
  arrives silently case-flattened to uppercase and auth always fails
  — looks exactly like a broken user database if you don't know to
  look here.
• Auto-wrap blank-line bug — see "Text rendering rules" above.
• Column-width overflow in list rendering (echo area names, file
  listings) on both 40- and 80-column screens needed independent
  fixes — width and overhead-per-row don't scale linearly.

See also

• docs/PORTS.md — port table
• docs/INSTALL.md §10 — enabling PETSCII40/PETSCII80
• docs/03-menus.md — the ANSI custom-menu system this deliberately
  does not share a tree with
• docs/24-game-center.md — the wider game catalog (Number Guessing
  is the only one also offered here)