Adds the four wire shapes Q#BP9 names, bumps the protocol to v21, and
factors the cell-grid validator so a panel frame shares the terminal's
rules without inheriting its PTY caps.
- `InstanceMessage::PanelFrame(PanelFramePayload)`, appended after
`InitialTargetResult`; `Absent` is an explicit authoritative state, not
silence, because the receiver retains its last valid frame.
- `FrontendEvent::{FrontendCellGeometry, PanelResizeRows, PanelPointer}`,
appended after `TerminalPointer`. Geometry is valid without a side
window — gating it on panel presence would deadlock the first open,
since the daemon needs columns before it can paint a first frame.
- `pmacs-protocol/src/wire_grid.rs` holds the shared rules: checked area,
visible-cell bound, cell count, cursor bounds, glyph legality,
wide-continuation topology, the aggregate glyph budget, and the
attachment rejection. The 512 per-axis caps, metadata, selection spans,
and the at_bottom/scroll_offset coupling stay terminal-only.
- The attachment rejection is deliberately shared despite its
terminal-side wording: panels render no attachments either, so sharing
it fails closed for both.
Both byte pins were falsified by revert: moving `PanelFrame` ahead of
`InitialTargetResult` shifts it 27 -> 28 and fails; moving the three
events ahead of `TerminalPointer` shifts it 12 -> 15 and fails.
The factoring changed no terminal acceptance — all 17 terminal tests pass
unchanged. It did surface a pre-existing coverage gap: those tests pin
the row cap but never the column cap, so widening `max_cols` to u32::MAX
left them green. `a_panel_wider_than_512_columns_is_legal_while_a_terminal_is_not`
now covers that direction.
The daemon projection, the epoch state machine, and the GPU band are
later slices of this stage.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RuhVYUPHXMHG8r2z4tsDPR
Levi Neuwirth
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